Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
CHAPTER 1 :Introduction to Electronic Communications •
the transmis transmission sion,, reception reception and processin processing g of informati information on between two or more locations using electronic circuits
electronic communications
•
signals that are time-varying voltages or currents that are cont contin inuo uous usly ly chan changi ging ng,, such such as cosi cosine ne and and sine sine wave waves. s. It contains an infinite number of values
analog signals
•
signals that are voltages or currents that change in discrete steps or levels
digital signals
•
Samu Samuel el Finl Finley ey Morse (1837)
he invented the first workable telegraph
•
it is used to transfer information in the form of dots, dashes and spaces between a simple transmitter and receiver using a transmission line consisting consisting of a length of metallic wire
•
they hey were the the firs firstt to succ succes ess sful fully tran ransfer fer huma human n conversation over a crude metallic-wire communication system using a device they called telephone
Bree Breese se
electromagnetic induction
Alexander Graham Bell Thomas A. Watson
a logarithmic unit that can be used to measure ratios of decibel (dB) virtually anything •
•
a transmission-measuring transmission-measuring unit used to express relative gains and losses of electronic devices and for describing relationships between signals and noise
decibel
•
attenuation
another name for power loss a collection of one or more electronic devices or circuits that • converts the original source information to a form more suitable for transmission over a particular transmission medium
transmitter
it prov provid ides es a mean means s of tran transp sport ortin ing g sign signal als s betw betwee een n a transmission medium or communications channel transmitter and a receiver and can be as simple as a pair of communications copper wires •
•
any any unwant unwanted ed elect electric rical al signal signals s that that interf interfere ere with with the information signal
system noise
a collection of electronic devices and circuits that accepts the transmitted signals from the transmission medium and then converts those signals back to their original form higher-frequency higher-frequency analog signal •
receiver
•
•
the process of changing one or more properties of the analog 1
carrier modulation
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
carrier in proportion with the information signal •
a system system in which which energy energy is transm transmitt itted ed and and receiv received ed in analog form, both the information and the carrier are analog signals
Analog Analog system
commun communica icatio tion n
•
it cove covers rs a broa broad d rang range e of comm commun unic icat ation ion tech techni niqu ques es including digital and digital radio
Digi Digita tall system
comm commun unic icat atio ion n
a true digital digital system system where digital digital pulses pulses are transferr transferred ed between two or more points in communication system
digital transmission
the the tran transm smit itta tall of digi digita tall lly y modu modula late ted d anal analog og carri carrier ers s between two or more points in communication system
digital radio
•
•
the information signal is analog and the amplitude of the carrier is varied proportional to the information signal
•
Ampl Amplit itud ude e (AM)
modu modula lati tion on
modu modula lati tion on
•
the frequency is varied proportional to the information signal
Freq Freque uenc ncy y (FM)
•
a circuit performing modulation in a transmitter
modulator
•
a carrier that has been acted on by an information signal
modulated wave modulated signal
the the reve revers rse e proc proces ess s of modu modula lati tion on and and conv conver erts ts the the modulated carrier back to the original information
or
•
it is often used to refer to a specific band of frequencies allocated a particular service
•
•
demodulation channel
intelligence signal
another name for information signal
•
the process of converting a frequency or band of frequencies to another location in the total frequency spectrum
frequency translation
•
it can propagate as a voltage or current along a metallic wire as emitted emitted radio radio waves through through free space space or as light light waves down an optical fiber
electromagnetic energy
simply the number of times a periodic motion such as sine wave of voltage or current occurs in a given period of time
frequency
an international international agency agency in control of allocating allocating frequencies and services with the overall frequency spectrum
International Telecommunications Union (UTI)
•
•
•
signals in the 30-Hz to 300-Hz range and include ac power distribution signals (60Hz) and low frequency telemetry signals
•
sign signal als s in the the 300300-Hz Hz to 3000 3000-H -Hz z rang range e and and incl includ ude e
2
Extremely frequencies
Voice frequencies
low
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
carrier in proportion with the information signal •
a system system in which which energy energy is transm transmitt itted ed and and receiv received ed in analog form, both the information and the carrier are analog signals
Analog Analog system
commun communica icatio tion n
•
it cove covers rs a broa broad d rang range e of comm commun unic icat ation ion tech techni niqu ques es including digital and digital radio
Digi Digita tall system
comm commun unic icat atio ion n
a true digital digital system system where digital digital pulses pulses are transferr transferred ed between two or more points in communication system
digital transmission
the the tran transm smit itta tall of digi digita tall lly y modu modula late ted d anal analog og carri carrier ers s between two or more points in communication system
digital radio
•
•
the information signal is analog and the amplitude of the carrier is varied proportional to the information signal
•
Ampl Amplit itud ude e (AM)
modu modula lati tion on
modu modula lati tion on
•
the frequency is varied proportional to the information signal
Freq Freque uenc ncy y (FM)
•
a circuit performing modulation in a transmitter
modulator
•
a carrier that has been acted on by an information signal
modulated wave modulated signal
the the reve revers rse e proc proces ess s of modu modula lati tion on and and conv conver erts ts the the modulated carrier back to the original information
or
•
it is often used to refer to a specific band of frequencies allocated a particular service
•
•
demodulation channel
intelligence signal
another name for information signal
•
the process of converting a frequency or band of frequencies to another location in the total frequency spectrum
frequency translation
•
it can propagate as a voltage or current along a metallic wire as emitted emitted radio radio waves through through free space space or as light light waves down an optical fiber
electromagnetic energy
simply the number of times a periodic motion such as sine wave of voltage or current occurs in a given period of time
frequency
an international international agency agency in control of allocating allocating frequencies and services with the overall frequency spectrum
International Telecommunications Union (UTI)
•
•
•
signals in the 30-Hz to 300-Hz range and include ac power distribution signals (60Hz) and low frequency telemetry signals
•
sign signal als s in the the 300300-Hz Hz to 3000 3000-H -Hz z rang range e and and incl includ ude e
2
Extremely frequencies
Voice frequencies
low
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
frequencies generally associated with human speech, standard telephone channels •
signals in the 3-kHz to 30-kHz range which include the upper end of the human hearing hearing range, range, speciali specialized zed government government and military system (submarine communications)
•
Very low frequencies
signals in the 30-kHz to 300-kHz 3 00-kHz range and used primarily for marine and aeronautical navigation
Low frequencies
• sign signal als s in the 300-k 300-kHz Hz to 3-MH 3-MHz z rang range e and and are are used used primar primarily ily for commer commercia ciall AM radio radio broadc broadcas astin ting g (535 (535 kHz to 1605 kHz)
Medium frequency
•
signals in the 3-MHz to 30-MHz range and are used for twoway way radio radio commun communica icatio tions, ns, Voice Voice of Ameri America ca and Radio Radio Fre Free e Europe broadcast, amateur radio and citizens band (CB) radio
High frequencies
•
signals signals in the 30-MHZ to 300-MHz 300-MHz and are used for mobile mobile radio, marine, and aeronautical communications, commercial FM broadcas broadcasting ting (88 MHz to 108 MHz), MHz), and commercia commerciall televisi television on broadcasting of channels channels 2 to 13 (54 MHz to 216 MHz) •
signa signals ls in the 300-MHz 300-MHz to 3-GHz 3-GHz range range and are used used by commercia commerciall televisi television on broadcas broadcasting ting of channels channels 14 to 83, land mobile mobile commun communica icatio tion n servic services, es, cellul cellular ar teleph telephone ones, s, certa certain in radar and navigation systems, and microwave and satellite radio systems •
Very high frequencies
Ultrahigh frequencies
signal in the 3-GHz to 30-GHz range used for microwave and satellite radio communication system
Superhigh frequencies
signals in the 30-GHz to 300-GHz range and seldom used for radio communication system
Extremely frequencies
•
Infrared
•
sign signal al in the the 0.30.3-TH THz z to 300-T 300-THz Hz electromagnetic electromagnetic radiation generally associated with heat
rang range. e. It refe refers rs to
high
the the leng length th that that one one cycl cycle e of an elec electr trom omag agne neti tic c wave wave occupies in space. It is inversely proportional to the frequency of wavelength the wave and directly proportional to the frequency of the wave and directly proportional to the velocity of propagation
•
•
speed of light the two most significant limitations on the performance of a • communication system
3 x 108 m/s noise bandwidth
simp simply ly the the diff differ eren ence ce betw betwee een n the the high highes estt and and lowe lowest st frequencies in the information
bandwidth of information signal
•
3
an
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
•
the difference between the highest and lowest frequencies that the channel will allow to pass through
bandwidth of a communication channel
a highly theoretical study of the efficient use of bandwidth to propag propagate ate inform informati ation on throug through h elect electron ronic ic commun communica icatio tions ns system
Information theory
•
a measu measure re of how much much inform informati ation on can can be propa propagat gated ed • thro throug ugh h a comm commun unic icat atio ions ns syst system em and and is a func functi tion on of Information capacity bandwidth and transmission time
simply the number of bits transmitted during one second and is expressed in bit per second
•
Bit rate
•
any any unde undesi sira rabl ble e elec electr tric ical al ener energy gy that that fall falls s with within in the the passband signal
Electrical noise
•
correlated
implies a relationship between the signal and the noise. Exist only when a signal is present
•
noise present all the time whether there is signal or not
uncorrelated
•
noise that is generated outside the device or circuit
external noise
natur naturall ally y occurr occurring ing electr electrica icall distur disturba bance nces s that that origin originate ate within Earth’s surface like lightning
Atmospheric noise
•
another name for atmospheric noise
Static electricity
•
frequency of atmospheric noise
30 MHz
•
•
consis consists ts of electr electrica icall signa signall that that origin originate ate from from outsid outside e Earth’s atmosphere
Extraterrestrial Extraterrestrial noise Deep-space noise
•
another name for extraterrestrial noise
•
continuously distributed throughout the galaxies
Cosmic noise
•
another name for cosmic noise
Black-body noise
•
simply noise that is produced by mankind
Man-made noise
•
another name for man-made noise
Industrial noise
•
electrical interference generated generated within a device or circuit
internal noise
•
caused by random arrival of carriers at the output element of an electr electroni onic c device device such such as diode, diode, field field effect effect transi transisto storr or Shot noise bipolar transistor
4
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA •
any modification to a stream of carriers as they pass from the input to the output of a device produces an irregular random variation •
the rapid and random movement of electrons within a conductor due to thermal agitation •
another names for thermal noise:
Transit-time noise
Thermal noise
white noise Brownian noise Johnson noise
occurs when unwanted harmonics of a signal are produced through nonlinear amplification
Harmonic distortion
•
integer multiples of the original signal
Harmonics
•
another name for harmonic distortion
Amplitude distortion
•
•
the generation of unwanted sum and difference frequencies produced when two or more signals mix in a nonlinear device
Intermodulation distortion
characterized by high-amplitude peaks of short duration in the total noise spectrum
Impulse noise
•
Interference
•
a form of external noise meaning to disturb or detract from
•
when information signals from one source produce frequencies that fall outside their allocated bandwidth and interfere with information signals from another source •
the ratio of the signal power level to the noise power level
Electrical interference
Signal-to-noise ratio
CHAPTER 2: Signal Analysis and Mixing •
the only two levels possible in a digital signal
binary signal
•
four-level signals
quaternary digital signal
the voltage- or current-time variations that can be represented by a series of sine or cosine waves •
Electrical signals
•
a waveform which repeats at a uniform rate
Periodic
•
a description of a signal with respect to time
Time domain
•
a time-domain instrument
Oscilloscope 5
power
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
•
an amplitude-versus-time representation of the signal
Signal waveform
a description of a signal with respect to its frequency
Frequency-domain representation
•
•
Spectrum analyzer
a frequency-domain instrument
any repetitive waveform that is comprised of Sinusoidal wave more than one harmonically related sine or cosine wave • any periodic waveform that is not a sinusoid such as square waves, rectangular waves and Complex wave triangular waves •
a French physicist and mathematician who used a mathematical series to analyze a complex periodic wave •
a mathematical tool that allows us to move back and forth between time and frequency domains. It is used in signal analysis to represent the sinusoidal components of non-sinusoidal periodic waveforms
Baron Jean Fourier
•
it describes the symmetry of a waveform in the time domain, that is, its relative position with respect to the horizontal (time) and vertical (amplitude) axes a periodic voltage waveform in symmetric about • vertical axis that have axes, or mirror, symmetry
Fourier analysis
•
a periodic voltage waveform that said to have point, or skew, symmetry •
Wave symmetry
Even symmetry
Odd symmetry
a periodic voltage waveform such that the waveform for the first half-cycle repeats itself Half-wave symmetry except with the opposite sign for the second half cycle •
a waveform consists of all the frequencies contained in the waveform and their respective amplitudes plotted in the frequency domain •
range of frequencies contained in the spectrum the difference between the highest and lowest • frequencies contained in the information the difference between the highest and lowest • frequencies that the channel will allow to pass through
Frequency spectrum
•
•
the rate at which energy is dissipated, delivered,
6
Bandwidth
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
or used and is a function of the square of the voltage or current
Electrical power
•
a time-domain signal is sampled at discrete times
Discrete Fourier transform
•
the computing time is proportional to n log 2n rather that n2
Fast Fourier series
it reduces the information capacity of the system • the process of combining two or more signals and is an essential process in electronic communications • two ways in which signals can be combined or mixed:
Bandlimiting
it occurs when two or more signals combine in a linear device, such as passive network or a smallsignal amplifier
Linear summing (linear mixing)
•
•
occurs when two or more signals are combined in a nonlinear device such as a diode or large-signal amplifier
Mixing
linearly nonlinearly
• •
•
Nolinear mixing
•
undesired harmonics
Harmonic distortion
•
desired harmonics
Frequency multiplication
CHAPTER 3 : Oscillators, Phase-Locked Loops, and Frequency Synthesizers to fluctuate between two states or conditions, to vibrate or to change •
•
Oscillator
a device that produces oscillations
an amplifier with a feedback loop (i.e., a path to propagate from the output back to input) •
•
Oscillate
four requirements for a feedback oscillator:
Feedback oscillators
• • •
•
•
an untuned oscillator RC phase shift oscillator that uses both positive and negative feedback
7
amplification positive feedback frequencydetermining components power source
Wien-bridge oscillator
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA •
LC oscillators
the ability of an oscillator to remain at a fixed frequency and is of primary importance in communication systems
Frequency stability
oscillator circuits that utilize tuned LC tank circuits for the frequency-determining frequency-determining components •
feedback oscillator circuits in which the LC tank circuit circuit is replaced replaced with a crystal crystal for the the frequencyfrequencydetermining component the study of the form, structure, properties, and • clas classi sifi fica cati tion ons s of crys crysta tals ls.. It deal deals s with with latt lattic ices es,, bonding and the behavior of slices of crystal material that have been cut at various angles with respect to the crystal’s axes •
it occurs occurs when when oscil oscillat lating ing mechan mechanica icall stress stresses es appli applied ed across across a crysta crystall latti lattice ce struct structure ure genera generate te electrical oscillations and vice versa
Crystal oscillators
Crystallography
•
•
Piezoelectric effect
Bulk Acoustic Waves (BAWs)
another name for mechanical vibrations
•
it is consist of a crystal-controlled oscillator and a voltage-variable voltage-variable component such as varactor diode
Crystal oscillator module
it is often used when when describin describing g varactor varactor diode fabrication
Graded junction
•
CHAPTER 4 : Amplitude Modulation Transmission •
the the proc proces ess s of impr impres essi sing ng lowlow-fr freq eque uenc ncy y information signal onto a high-frequency
Modulation
the reverse process where the received signals are transformed back to their original form
Demodulation
•
the the proc proces ess s of chan changi ging ng the the ampl amplit itud ude e of a relatively high frequency carrier signal in proportion with with the instan instantan taneou eous s value value of the modula modulatin ting g signal freq requencies that are high enough to be • efficiently radiated by an antenna and propagated through free space •
•
the most commonly used amplitude modulation
a term used to describe the amount of amplitude change present in an AM waveform
•
8
Amplitude Modulation (AM)
Radio frequency
AM double side-band full carrier (AM DSBFC) Coefficient of modulation
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
gives the percentage change in the amplitude of the output wave when the carrier is acted on by a Percent modulation modulating signal •
it use a unique arrangement of transistors and FETs FETs to perfor perform m signa signall multip multiplic licati ation, on, which which is a characte characteristi ristic c that makes them ideally suited for generating AM waveforms •
Linear Linear integrate integrated-cir d-circuit cuit function generators
•
Preamplifier
a low-gain, high-input impedance linear amplifier used to isolate isolate the oscillat oscillator or from the high-powe high-powerr amplifiers
Buffer amplifier
typi typica call lly y a sens sensit itiv ive e clas class s A line linear ar volt voltag age e amplifier with a high input impedance
•
it is some someti time mes s call called ed upwa upward rd or down downwa ward rd modulation and has absolutely nothing to do with the frequency of the carrier. A form of amplitude distortio distortion n introduced introduced when positive positive and negative negative alter alterna natio tions ns in the AM modula modulated ted signa signall are not equal •
Carrier shift
•
Nonsinusoidal signals
are are comp comple lex x wave waves s made made up of two two or more more harmonically related sine waves and include square, rectangular and triangular waves
Complex repetitive
a form of amplitude modulation where signals from two separate information sources modulate the same carrier carrier frequency frequency at the same time without without interfering with each other
Quad Quadra ratu ture re modulation
are comple complex x wavef waveform orms s compri comprised sed of two or more frequencies •
•
ampl amplit itud ude e
CHAPTER 5 : Amplitude Modulation Reception several parameters commonly used to evaluate the ability of a receiver to successfully demodulate a radio signal •
• • • • • • •
selectivity bandwidth sensitivity dynamic range fidelity insertion loss noise temperature
a receiver parameter that is used to measure the ability of the receiver to accept a given band of Selectivity frequencies and reject all others
•
•
the noise reduction ratio achieved by reducing 9
Bandwidth Improvement
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
(BI)
the bandwidth • the corresponding reduction in the noise figure to the reduction in bandwidth
the minim inimum um RF signa ignall lev level tha that can can be dete detect cted ed at the the inpu inputt to the the rece receiv iver er and and stil stilll produce a usable demodulated information signal • another name for receiver sensitivity
Noise Figure Improvement
•
the difference in decibels between the minimum input input level level necessa necessary ry to discer discern n a signa signall and and the inpu inputt leve levell that that will will over overdr driv ive e the the rece receiv iver er and and produce distortion
Sensitivity Threshold
•
the outp outpu ut powe ower when hen the the RF ampli mplifi fier er respon response se is 1 dB less less than than the ideal ideal linear linear-ga -gain in response • a measur measure e of the ability ability of a commun communica icatio tion n system to produce at the the output of the receiver, an exact replica of the original source information •
three forms of distortion that can deteriorate the fidelity of a communication system: •
Dynamic range
1-dB compression point
Fidelity
• • •
•
the predominant cause of phase distortion
the total total phase phase shift shift encoun encounter tered ed by a signa signall • and and can can gene genera rall lly y be tole tolera rate ted d as long long as all all frequ frequenc encies ies underg undergo o the same same amoun amountt of phase phase delay • it occurs occurs when when differ different ent freque frequenci ncies es underg undergo o different phase shifts and may have a detrimental effect on a complex waveform
amplitude frequency phase
Filtering
Absolute phase shift
Differential phase shift
• it occurs when the amplitude-versus-frequency characteristics characteristics of a signal at the output of a receiver differ from those those of the original information signal signal
Amplitude distortion
it occurs occurs when when freque frequenci ncies es are prese present nt in a received signal that were not present in the original source information
Frequency distortion
•
a parame parameter ter assoc associat iated ed with with the freque frequenci ncies es • that that fall fall with within in the the pass passba band nd of a filt filter er and and is gener enera ally lly defi efined ned as the the rati ratio o of the the powe ower transferred to a load with a filter in the circuit to the power transferred to a load without the filter a hypoth hypotheti etical cal value value that that cannot cannot be direct directly ly • measur measured. ed. An indica indicatio tion n of the reduct reduction ion in the signal-t signal-to-noi o-noise se as a signal signal propagates propagates through through a receiver 10
Insertion Loss (IL)
Equivalent Noise Temperature (T e)
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
• •
two basic types of radio receivers: •
a type type of rece receiv iver er wher wherei ein n the the freq freque uenc ncy y generated in the receiver and used for demo demodu dula lati tion on are are sync synchr hron oniz ized ed to osci oscill llat ator or frequencies generated in the transmitter
coherent (synchronous) noncoherent (asynchronous)
•
a type of receiver where either no frequencies are genera generated ted in the recei receiver ver or the freque frequenci ncies es used for demodulation are completely independent from the transmitter’s carrier frequency
Coherent
•
anoth nother er name name for for nonc noncoh oher eren entt dete detect ctio ion n beca becaus use e the the info inform rmat atio ion n is reco recove vere red d from from the the received waveform by detecting the shape of the modulated envelope
Noncoherent
•
Envelope detection
one of the earliest types of AM receivers and probab probably ly the simpl simplest est desig designed ned radio radio receiv receiver er available
Tuned Radio-frequency (TRF)
it means to mix two frequencies together in a nonlinear device or to translate one frequency to another using nonlinear mixing
Heterodyne
•
•
•
five sections of the superheterodyne receiver:
• • • • •
a broad-tuned bandpass filter with an adjustable center frequency that is tune to the desired carrier frequ frequenc ency. y. It reduc reduce e the noise noise bandwi bandwidth dth of the receiver •
•
it determines the sensitivity of the receiver
RF section Mixer/converter section IF section Audio detector section Audio amplifier section
Preselector
RF amplifier
• its purpose is to convert the IF signals back to the original source
Detector
the ability of the local oscillator in a receiver to oscillate either above or below the selected radio freq freque uenc ncy y carr carrie ierr by an amou amount nt equa equall to the the intermediate frequency throughout throughout the entire radio frequency band • the difference between the actual local oscillator frequency and the desired frequency
Tracking
•
•
any any frequ frequenc ency y other other than than the selec selected ted radio radio 11
Tracking error
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
frequency carrier that if allowed to enter a receiver and mix with the local oscillator will produce a cross-product frequency that is equal to the intermediate frequency a numerical measure of the ability of a • preselector to reject the image frequency
Image frequency
it occurs when a receiver picks up the same station at two nearby points on the receiver tuning dial its purpose is to down-convert the incoming • radio frequencies to intermediate frequencies
Double spotting
•
the most common technique used for coupling IF amplifiers where the voltage that is applied to the primary windings of a transformer is transferred to the secondary windings
Image-frequency ratio
rejection
Mixer / converter
•
Inductive coupling
or
transformer
•
the ability of a coil to induce a voltage within its own windings
Self-inductance
•
the ability of one coil to induce a voltage in another coil
Mutual inductance
the ratio of the secondary flux to the primary flux • the transfer of flux from the primary to the secondary windings
Coefficient of coupling
a circuit that compensates for minor variations in the received signal level where it automatically increases the receiver gain weak RF input levels and automatically decreases the receiver gain when a strong RF signal is received when the receiver becomes less sensitive •
Automatic Gain Control (AGC)
•
a circuit that has the purpose to quiet a receiver in the absence of a received signal. It keeps the audio section of the receiver turned off or muted in the absence of a received signal
Squelch circuit
used for removing sporadic, high amplitude noise transients of short duration such as impulse noise another circuit option commonly used for • reducing the effects of high amplitude noise pulses where it detects the occurrence of a high-amplitude, short duration noise spike then mutes the receiver by shutting off a portion of the receiver for the duration of the pulse
Diode limiters or clippers
the ratio of the demodulated signal level at the output of the receiver to the RF signal level at the input to the receiver
Net Receiver Gain
•
•
•
•
12
Flux linkage
Automatic desensing
Blanking circuit
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
•
samples of receiver losses:
• • •
preselector loss mixer loss detector loss
•
System gain
the adjustment for the center frequency of the preselector and the adjustment for the local oscillator
Gang tuned
it includes all the gains and losses incurred by a signal as it propagates from the transmitter output stage to the output of the detector in the receiver and includes antenna gain and transmission line and propagation losses •
it offers higher gain and less noise than conventional cascaded amplifiers •
Cascoded amplifier
CHAPTER 6 Single-Sideband Communications System a form of amplitude modulation in which the AM Single-sideband Full Carrier (SSBFC) carrier is transmitted at full power but only one of the sidebands is transmitted. It requires only half as much bandwidth as conventional double sideband AM •
•
a form of amplitude modulation in which the carrier is totally suppressed and one of the sidebands removed and considerably less transmitted power
AM Single-sideband Suppressed Carrier (SSBSC)
•
a form of amplitude modulation in which one sideband is totally removed and the carrier voltage is reduced to approximately 10% of its unmodulated amplitude
AM Single Side-band Reduced Carrier (SSBRC)
a form of amplitude modulation in which a single carrier frequency is independently modulated by two different modulating signals
AM Independent Sideband (ISB)
•
13
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
a form of amplitude modulation in which the carrier and one complete sideband are transmitted but only part of the second sideband is transmitted •
the rms power developed at the crest of the modulation envelope when the modulating-signal frequency components are at their maximum amplitudes
AM Vestigial Sideband (VSB)
•
Peak envelope power (PEP)
• •
advantages of single-sideband transmission:
• • •
•
disadvantages of single-sideband transmission:
• •
a circuit that produces suppressed-carrier signal •
•
a
double-sideband
complex receivers tuning difficulties
Balanced Modulator
Balanced Lattice Modulator
another name for balanced modulator
a small carrier component always present in the output signal •
•
power conservation bandwidth conservation selective fading noise reduction
the typical amount of carrier suppression
three transmitter configurations used for singlesideband generation: •
Carrier Leak
between 40 dB and 60 Db • • •
it is made from lead zirconate-titanate which exhibits the piezoelectric effect •
a mechanically resonant transducer that when it receives electrical energy, it converts to mechanical vibrations and then converts the vibrations back to electrical energy at its output
phase-shift method filter method third method
Ceramic filters
•
•
four elements that comprise a mechanical filter:
Mechanical filter
• •
• •
filters that use acoustic energy rather than electromechanical energy to provide excellent performance for precise bandpass filtering
input transducer series of mechanical resonant metal disks coupling rod output transducer
•
•
Surface Acoustic Wave (SAW) filters Bidirectional
the basic SAW filter
14
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
it launches the acoustic wave in only one direction a narrow band PLL that tracks the pilot carrier in • the composite SSBRC receiver signal and uses the recovered carrier to regenerate coherent local oscillator frequencies in the synthesizer
Unidirectional
a system that provide narrowband voice communications for land-mobile services with nearly the quality achieved with FM systems and do it using less than one-third the bandwidth
Amplitude-compandoring Single-sideband (ACSSB)
•
•
a device expansion •
that
performs
compression
and
Recovery circuit
Compandor (compressor-expander)
•
process of combining transmissions from more than one source and transmitting them over a common facility, like metallic or optical fiber cable or a radio-frequency channel an analog method of combining two or more • analog sources that originally occupied the same frequency band in such a manner that the channels do not interfere with each other a multiplexing method that uses doublesideband suppressed-carrier transmission to combine two information sources into a single composite waveform that is then transmitted over a common facility without the two channels interfering with each other
Multiplexing
Frequency-division Multiplexing (FDM)
•
Quadrature Multiplexing (QM)
CHAPTER 7 Angle Modulation Transmission it results whenever the phase angle modulation of Angle modulation a sinusoidal wave is varied with respect to time •
varying the frequency of a constant-amplitude carrier directly proportional to the amplitude of the modulating signal at a rate equal to the frequency of the modulating signal •
Direct Frequency Modulation (FM)
varying the phase of a constant-amplitude carrier directly proportional to the amplitude of the Direct modulating signal at a rate equal to the frequency of (PM) the modulating signal •
•
the relative angular displacement of the carrier phase in radians in respect to the reference phase •
the relative displacement of the carrier frequency 15
Phase
Modulation
Phase deviation (Δθ)
Frequency deviation (Δf)
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
in hertz in respect to its unmodulated value •
four terms with reference to angle-modulation
•
• •
•
instantaneous phase deviation instantaneous phase instantaneous frequency deviation instantaneous frequency
•
the instantaneous change in the phase of the carrier at a given instant of time and indicates how much the phase of the carrier is changing with respect to its reference phase
Instantaneous deviation
the precise phase of the carrier at a given instant of time
Instantaneous phase
•
the instantaneous change in the frequency of the carrier and is defined as the first time derivation of Instantaneous deviation the instantaneous frequency deviation
phase
•
frequency
the precise frequency of the carrier at a given Instantaneous frequency instant of time and is defined as the first derivative of the instantaneous phase it can be defined as angle modulation in which the Phase modulation • instantaneous phase deviation is proportional to the amplitude of the modulating signal voltage and the instantaneous frequency deviation is proportional to the slope or first derivative of the modulating signal •
•
an angle modulation in which the instantaneous frequency deviation is proportional to the amplitude of the modulating signal and the instantaneous phase deviations is proportional to the integral of the modulating signal voltage
Frequency modulation
•
the output-versus-input transfer functions for the modulators which give the relationship between what output parameter changes in respect to specified changes in the input signal
Deviation sensitivities
peak phase deviation • the change in frequency that occurs in the carrier when it is acted on by a modulating-signal frequency
Modulation index Frequency deviation
•
•
Carrier swing
peak-to-peak frequency deviation
•
the ratio of the frequency deviation actually produced to the maximum frequency deviation allowed by law stated in percent form
Percent Modulation
a circuit in which the carrier is varied in such a way that its instantaneous phase is proportional to
Phase modulator
•
16
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
the modulating signal •
Unmodulated carrier (rest frequency)
a single-frequency sinusoid
a circuit in which the carrier is varied in such a way that its instantaneous phase is proportional to the integral of the modulating signal •
Frequency modulator (frequency deviator)
•
differentiator followed by an FM modulator
PM Modulator
•
FM demodulator followed by an integrator
PM demodulator
•
integrator followed by a PM modulator
FM modulator
•
PM demodulator followed by a differentiator
FM demodulator
rule that approximates the bandwidth necessary to transmit an angle-modulated wave as twice the sum of the peak frequency deviation and the highest modulating-signal frequency, it defines a bandwidth that includes approximately 98% of the total power in the modulated wave •
Carson’s rule
the worst-case modulation index and is equal to the maximum peak frequency deviation divided by the maximum modulating-signal frequency
Deviation Ratio (DR)
the interference produced when the highest side frequencies from one channel are allowed to spill over into adjacent channels
Adjacent Channel Interference
•
•
the noise voltage at the output of a PM demodulator is constant with frequency, whereas the noise voltage at the output of an FM demodulator increases linearly with frequency •
Noise Triangle
•
a high-pass filter
Preemphasis Network
•
a low-pass filter
Deemphasis Network
•
an angle modulation in which the frequency of the carrier is varied directly by the modulating signal
Direct FM
an angle modulation in which the frequency of the carrier is deviated indirectly by the modulating signal
Direct PM
•
a circuit that compares the frequency of the noncrystal carrier oscillator to a crystal reference oscillator and then produces a correction voltage proportional to the difference between two frequencies •
•
a purpose to achieve near-crystal stability of the 17
Automatic Control (AFC)
Frequency
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
transmit carrier without using a crystal in the carrier oscillator • meaning cancel of the deviation thus removing the modulation from the FM wave
AFC loop
transmitters that produce an output waveform in which the phase deviation is directly proportional to the modulating signal therefore the carrier oscillator can be a crystal because the oscillator itself is not a modulator
Indirect FM transmitters
•
wipe off
•
the low-pass filter that is simply 1/f filter
Predistorter (frequency correction network)
•
advantages of angle modulation:
• • • •
it allows a receiver to differentiate between two signal received with the same frequency •
noise immunity FM thresholding capture effect power utilization efficiency
Capture effect
CHAPTER 8 : Angle Modulation Reception and FM Stereo •
Preselector
it rejects the image frequency
it establishes the signal-to-noise ratio and noise figure •
•
RF amplifier
Mixer/converter
down-converts RF to IF
•
it provides most of the gain and selectivity of the receiver
IF amplifiers
it removes the information from the modulated wave
Detector
•
18
and
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
it is a frequency-dependent circuits designed to produce an output voltage that is proportional to the instantaneous frequency at its input •
the most common circuits used for demodulating FM signal •
it converts FM to AM and then demodulate the AM envelope with conventional peak detectors •
FM Demodulators
slope detector Foster-Seeley • discriminator ratio detector • PLL demodulator • quadrature detector • tuned-circuit frequency discriminators •
•
it is the simplest form of tuned-circuit frequency discriminators that has the most nonlinear voltageversus-frequency characteristics
Single-ended slope detector
•
a simply two single-ended slope detectors connected in parallel and fed 180º out of phase
Balanced slope detector
•
a tuned-circuit frequency discriminator whose operation is very similar to that of the balanced slope detector
Foster-Seeley discriminator (phase shift discriminator)
•
it is relatively immune to amplitude variations in its input signal, it has a single tuned circuit in the transformer secondary
Ratio Detector
it requires no tuned circuits and automatically compensates for changes in the carrier frequency due to instability in the transmit oscillator
Phase-Locked Loop FM Demodulator
it extracts the original information signal from the composite IF waveform by multiplying two quadrature (90º out of phase) signals
Quadrature FM Demodulator (coincidence detector)
the minimum dB difference in signal strength between two received signals necessary for the capture effect to suppress the weaker signal
Capture Ratio
•
•
(PLL)
•
the inherent ability of FM to diminish the effects of Capture Effect interfering signals •
it is used rather than a simple mechanical switch to reduce the static noise associated with contact bounce in a mechanical switches •
Electronic push-to-talk (PTT)
CHAPTER 9: Digital Modulation •
the transmission, reception, and processing of Electronic communications
19
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
information with the use of electronic circuits the transmittal of digitally modulated analog signals (carriers) between two or more points in a communication system •
sometimes called for digital modulation because digitally modulated signals can be propagated through Earth’s atmosphere and used in wireless communications systems
Digital modulation
•
Digital radio
a digitally modulated signal where in the information signal is digital and the amplitude of the carrier is varied proportional to the information signal
Amplitude (ASK)
Shift
Keying
•
if the frequency is varied proportional to the information signal
Frequency (FSK)
Shift
Keying
if the phase of the carrier is varied proportional to the information signal
Phase Shift Keying (PSK)
•
•
a highly theoretical study of the efficient use of bandwidth to propagate information through Information theory electronic communications systems •
a measure of how much information can be propagated through a communication system and is a function of bandwidth and transmission time •
Information capacity
•
the most basic digital symbol used to represent information
Binary digit, bit
•
Bit rate
simply the number of bits transmitted during one second and is expressed in bits per second (bps) •
he published a paper in the Bell System Technical Journal relating the information capacity of a Claude E. Shannon, 1948 communication channel to bandwidth and signal-tonoise ratio •
M-ary
a term derived from the word binary
a term that is often misunderstood and commonly confused with bit rate (bps). Like bit rate, is also a Baud rate of change; however it refers to the rate of change of a signal on the transmission medium after encoding and modulation have occurred •
•
another name for amplitude-shift keying
Digital Amplitude Modulation (DAM)
•
a form of constant-amplitude angle modulation
Frequency-Shift Keying
20
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
similar to standard frequency modulation except the modulating signal is a binary signal that varies between two discrete voltage levels rather than a continuously changing analog waveform
(FSK)
the most common circuit used for demodulating binary FSK signals
Phase-locked Loop (PLL)
•
•
another form of angle-modulated, constantamplitude digital modulation; an M-ary digital modulation scheme similar to conventional phase modulation except with PSK the input is a binary digital signal and there are a limited number of output phases possible simplest form of PSK; a form of square-wave modulation of a continuous wave signal •
•
other names for BPSK:
Phase-shift Keying (PSK)
Binary Phase-shift (BPSK) •
•
Keying
phase reversal keying (PRK) biphase modulation
it acts as a phase reversing switch in a BPSK Balanced modulator transmitter •
•
similar to a phasor diagram except that the entire phasor is not drawn, only the relative positions of the peaks of the phasors are shown
Constellation diagram, sometimes called signal state-space diagram
•
a balanced modulator wherein the output signal is the product of the two input signals
Product modulator
•
Quaternary Phase Keying (QPSK), Quadrature PSK
another form of angle-modulated constantamplitude digital modulation. An M-ary encoding scheme where N = 2 and M = 4; four output phases are possible for a single carrier frequency •
Shift or
Dibits
group of two bits
a modified form of QPSK where the waveforms on the I and Q channels are offset or shifted in phase from each other by one-half of a bit time
Offset QPSK (OQPSK)
•
a bit in QPSK transmitter that modulates a carrier that is in phase with the reference oscillator
I bit (hence the name “I” for “in phase” channel)
a bit in QPSK transmitter that modulates a carrier that is 90° out of phase or in quadrature with the reference carrier
Q bit (hence the name “Q” for “quadrature” channel)
•
•
three bits are encoded, forming bits, forming tribits and producing eight different output places; there are eight possible output phases •
•
a code used to reduce the number of transmission 21
8-PSK
Gray
code
(maximum
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
errors
distance code)
•
a form of digital modulation similar to PSK except the digital information is contained in both the amplitude and the phase of the transmitted carrier; amplitude and phase-shift keying are combined; this reduce the likelihood or error occurring
Quadrature-amplitude Modulation (QAM)
less bandwidth is required to propagate a given bit rate
Bandwidth compression
•
efficiency often used to compare the performance of one Bandwidth density or digital modulation technique to another; the ratio of (information the transmission bit rate to the minimum bandwidth spectral efficiency) required for a particular modulation scheme •
the process of extracting a phase-coherent reference carrier from a receiver signal •
Carrier recovery referencing)
(phase
the binary data were encoded as a precise phase Absolute Phase Encoding of the transmitted carrier • the function to determine the absolute phase of Carrier Recovery Circuit the received carrier necessary to produce a carrier at the receiver that is phase coherent with the transmit reference oscillator •
•
methods of carrier recovery
• • •
an alternative form of digital modulation where the binary input information is contained in the difference between two successive signaling elements rather than the absolute phase •
squaring loop Costas loop remodulator
Differential Keying (DPHK)
Phase-sift
combines encoding and modulation to reduce the Convolutional (tree) codes probability of error, thus improving the bit error performance •
•
the manner in which signal-state transitions are allowed to occur, and transitions that do not follow this pattern are interpreted in the receiver as transmission errors
Trellis Coding
an encoding technique used for over standard telephone circuits the ratio of the average carrier power (the • combined power of the carrier and its associated sidebands)
Trellis Code Modulation (TCM) Carrier-to-noise Power Ratio
•
•
Energy per bit
the energy of a single bit of information
the thermal noise power normalized to a 1-Hz bandwidth •
22
Noise power density
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
•
used to compare two or more digital modulation systems that use different transmission rates (bit rates) modulation schemes
Energy per Power Density
Bit-to-noise
simply the ratio of the energy of a single bit to the noise power present in 1 Hz of bandwidth
Energy per Power Density
Bit-to-noise
•
•
Antipodal signaling
optimum signaling format
•
the transmitter and receiver are not frequency or phase synchronized
Noncoherent FSK
local receiver reference signals are in frequency and phase lock with the transmitted signals
Coherent FSK
•
CHAPTER 10: Digital Transmission •
primary advantage of digital transmission
Noise immunity
•
the processing of analog signals using digital methods and includes bandlimiting the signal with filters, amplitude equalization, and phase shifting
Digital (DSP)
•
one of the most important aspects of any communications system because it is costly and limited
Bandwidth
consists essentially of sampling analog information signals and then converting those samples into discrete pulses and transporting the pulses from a source to a destination over a physical transmission medium
Pulse Modulation
•
Signal
Width sometimes called pulse duration modulation Pulse (PWM) (PDM) or pulse length modulation (PLM), as the width of a constant amplitude pulse is varied proportional to the amplitude of the analog signal at the time the signal is sampled •
the position of a constant-width pulse within a prescribed time slot is varied according to the amplitude of the sample of the analog signal •
Processing
Modulation
Pulse Position Modulation (PPM)
the amplitude of a constant width, constant- Pulse Amplitude Modulation position pulse is varied according to the amplitude of (PAM) the sample of the analog •
23
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
•
the analog signal is sampled and then converted to a serial n-bit binary code for transmission; each code has the same number of bits and requires the same length of time transmission
Pulse (PCM)
Code
Modulation
•
he is credited with inventing PCM in 1937 while working for AT&T at its Paris laboratories
Alex H. Reeves
•
the function to periodically sample the continually changing analog input voltage and convert those samples to a series of constant-amplitude pulses that can more easily be converted to binary PCM code
Sampling circuit in a PCM transmitter
•
when tops of the sample pulses retain their natural shape during the sample interval making it difficult for an ADC to convert the sample to a PCM code
Natural Sampling
introduces less aperture distortion than natural sampling and requires a slower analog-to-digital converter
Flat-top sampling
•
•
the gradual discharge across the capacitor during conversion time caused by the capacitor discharging through its own leakage resistance and the input impedance of voltage follower
Droop
•
establishes the minimum sampling rate (f s) that can be used for a given PCM system
Nyquist sampling theorem
an impairment that occurs if minimum Nyquist sample rate is less than two times maximum analog input frequency
Alias or foldover distortion
•
the process of converting an infinite number of Quantization possibilities to a finite number of conditions •
type of code wherein the codes on the bottom half Folded binary code of the table are a mirror image of the codes on the top half, except for the sign bit •
•
the magnitude difference between adjacent steps
it occurs if the magnitude of the sample exceeds the highest quantization interval •
•
Quantization Quantum Overload limiting)
interval
distortion
(peak
Resolution
the magnitude of a quantum
any round-off errors in the transmitted signal are reproduced when the code is converted back to analog in the receiver •
24
or
Quantization Error (Qe )
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
another name for quantization error • the ratio of the largest possible magnitude to the smallest possible magnitude that can be decoded by the digital-to-analog converter in the receiver •
Quantization Noise (Qn ) Dynamic Range (DR)
a numerical indication of how efficiently a PCM Coding Efficiency code is utilized; the ratio of the minimum number of bits required to achieve a certain dynamic range to the actual number of PCM bits used •
the magnitude change successive code is the same •
between
any
two
occurs when the input signal is at its minimum amplitude •
during times when there is no analog input signal, the only input to the PAM sampler is random, thermal noise •
Linear codes
Signal voltage-toquantization noise voltage ratio (SQR) Idle Channel Noise
•
the first quantization interval is made larger in amplitude than the rest of the steps
Midtread quantizing
•
the lowest-magnitude positive and negative codes have the same voltage range bas all the other codes
Midrise quantization
•
this type of coding compares the PAM signal to a ramp waveform while a binary counter is being advanced at a uniform rate; it requires a very fast clock
Level-at-a-time coding
•
this type of coding determines each digit of the PCM code sequentially; analogous to a balance where known reference weights are used to determine an unknown weight
Digit-at-a-time coding
flash encoders and are more complex; however they are more suitable for high-speed applications
Word-at-a-time coding
•
•
the process of compressing and then expanding
Companding
•
amplified less than the lower-amplitude signals
Compressed
•
amplified more than the lower-amplitude signals
Expanded
•
Analog expansion
it involves compression in the transmitter after the input sample has been converted to a linear PCM code and then expansion in the receiver prior to PCM decoding
Digital companding
it was implemented with diodes that were placed just after the low-pass filter in the PCM receiver •
25
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA •
a single integrated-circuit chip function to encode and decode
Codec
•
refers to the most of the more recently developed codecs as they include an antialising (bandpass filter), a sample-and-hold circuit, and an analog-to-digital converter in the transmit section and a digital-toanalog converter, a hold circuit, and a bandpass filter in the receive section
Combo chips
special voice encoders/decoders; are designed to reproduce only the short-term power spectrum, and the decoded time waveforms often only vaguely resemble the original input signal
Vocoders
•
•
three vocoding techniques:
• • •
•
channel vocoder formant vocoder linear predictive coder
Homer Dudley, 1928
he developed the first channel vocoder
•
the spectral power of most speech energy concentrates at three or four peak frequencies
Formants
•
a vocoder that compressed conventional speech waveforms into an analog signal with a total bandwidth of approximately 300 Hz
First channel vocoder
•
a vocoder that takes advantage of the fact that the short term spectral density of typical speech signals seldom distributes uniformly across the entire voice-band spectrum; it simply determines the location of
Format vocoders
•
a vocoder that extracts the most significant portions of speech information directly from the time waveform rather than from the frequency spectrum as with the channel and formant vocoders
Linear predictive coders
•
simply the data rate at which serial PCM bits are locked out of the PCM encoder onto the transmission line; it is dependent on the sample rate and the number of bits in the compressed PCM code
Line speed
it uses a single-bit PCM code to achieve digital transmission of analog signals the slope of the analog signal greater than the • delta modulator
Delta modulation
•
Slope overload
when the original analog input signal has a Granular noise relatively constant amplitude, the reconstructed signal has variation that were not present in the original signal a delta modulation system where the step size of Adaptive delta modulation • •
26
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
the DAC is varied, depending on the amplitude characteristic of the analog signal • secondary lobes
Ringing tails
an important consideration in the transmission of Intersymbol pulses over circuits with a limited bandwidth and a (ISI) nonlinear phase response •
•
it equalize the distortion for all frequencies, creating a uniform transmission medium and reducing transmission impairments
Equalizers
•
placed in a communication channel to bandlimit signals and reduce or eliminate predicted noise and interference; also used to produce specific pulse response
Filters
it resulted when the frequency characteristics of a communication channel depart from the normal or expected values; occurs when the peaks of pulses are reduced causing improper ringing frequencies in the time domain
Pulse distortion
•
simply the superposition of harmonically related sine waves amplitude and phase relationships •
interference
a series of Pulse with specific
•
it occurs if the relative phase relations of the individual sine waves are altered
Phase distortion
a convenient technique for determining the effects of the degradations introduced into the pulses as they travel to the regenerator
Eye pattern
•
CHAPTER 11 : Digital T- Carriers and Multiplexing •
the transmission of information from one or ore source to one or more destination over the same transmission medium; the transmission medium may be a metallic wire pair, a coaxial cable, a PCS mobile telephone, a terrestrial microwave radio system, a satellite microwave system, or an optical fiber cable
Multiplexing
•
a rather unsophisticated form of multiplexing that simply constitutes propagating signals from different sources on different cables that are contained within the same trench
Space-division multiplexing (SDM)
transmissions from multiple sources occur on the same facility but not at the same time; transmissions
Time division multiplexing
•
27
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
from various sources are interleaved in the time domain •
a communication system that uses digital pulse rather than analog signals to encode information
Digital carrier
•
stands for transmission one and specifies a digital carrier system using PCM-encoded analog signals
T1
occurs once per frame and is recovered in the receiver where it is used to maintain frame and sample synchronization between the TDM transmitter and receiver
Additional bit (framing bit)
•
consists of 24 193-bit frames totaling 4632 bits, of Extended format which 24 are bits •
a digital interface that provides the physical connection to a digital carrier network •
•
can handle bit-rate conversions on both directions
provides a convenient place to make patchable interconnects and perform routine maintenance and troubleshooting •
superframe
Data service unit/channel service unit (DSU/CSU) Multiplexers/demultiplexers (muldem) Digital cross-connect (DSX)
•
a low-quality video transmission for use between nondedicated subscribers
Picturephone
involves converting standard logic levels to a form more suitable to telephone line transmission
Digital line encoding
•
•
can be used to categorize the type of transmission
Duty cycle
•
if the binary pulse is maintained for the entire bit time
Nonreturn to zero (NRZ)
•
if the active time of the binary pulse is less than 100% of the bit time
Return to zero (RZ)
•
a condition when a long string of either logic 1s or 0s produces a condition in which a receive may lose its amplitude reference for optimum discrimination between received 1s and 0s
DC wandering
•
a popular type of line encoding that produces a strong timing component for clock recovery and does not cause dc wandering
Digital (Manchester diphase)
used for encoding SMPTE (Society of Motion Picture and Television Engineers) time-code data for recording on videotapes
Biphase M
•
28
biphase code or
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
•
forms of delay-modulated codes where a logic 1 condition produces a transition in the middle of the clock pulse and a logic 0 produces no transition at the end of the clock intervals unless followed by another logic 0
Miller codes
•
used for the transmission of PCM-encoded timedivision multiplexed digital signals
T carriers
filters and shapes the incoming digital signal and raises its power level so that the regenerator circuit can make a pulse-no pulse decision
Amplifier/equalizer
•
reproduces the clocking information from the Timing clock recovery received data and provides the proper timing information to0 the regenerator •
•
simply a threshold detector that compares the sampled voltage received to a reference level and determines whether the bit is a logic 1 or logic 0
Regenerative repeater
•
were designed to combine PCM and TDM techniques for short-haul transmission of 24 64-kbps channels with each channel capable of carrying digitally encoded voice-band telephone signals or data
T1 carrier systems
•
a technique used to ensure that sufficient transitions occur in the data to maintain clock synchronization
Binary eight substitution (B8ZS)
the same as added-digit framing except that digits are added in groups or words instead of as individual bits
Added-channel framing
•
•
2 methods of interleaving PCM transmissions:
• •
bit interleaving word interleaving
•
a large-scale integration chip designed for use in the telecommunications industry for private branch exchanges, central office switches, digital handsets, voice store-and-forward systems and digital echo suppressors
Codec
combined codec chips; provide the analog-todigital and the digital-to-analog conversions and the transmit and receive filtering necessary to interface a full-duplex (four wire) voice telephone circuit to the PCM highway of a TDM carrier system
Combo chip
•
•
multiple sources that originally occupied the same
29
Frequency-division
zero
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
frequency spectrum are each converted to a different frequency band and transmitted simultaneously over a single transmission medium
multiplexing (FDM)
describes the modulating signal (intelligence) in a communications system
Baseband
•
•
a double side-band suppressed carrier modulator
Balanced modulator
•
a void band of frequencies that is not included within any supergroup band
Guard bands
•
involves the transmission of multiple digital signal using several wavelengths without their interfering with one another
Wavelength division multiplexing (WDM)
•
separate signals with different wavelengths in a manner similar to the way filters separate electrical signals of different frequencies
Demultiplexers or splitters
•
direct signals of a particular wavelength to a specific destination while not separating while not separating all the wavelengths present on the cable
WDM routers
•
specific wavelengths are separated from the other optic signal by reflecting them at different angles
Diffraction prisms
a mirror with a surface that has been coated with a material that permits light of only one wavelength to pass through while reflecting all other wavelengths
Dichroic filter
•
gratings
or
CHAPTER 12: Metallic Cable Transmission Media •
two general category of transmission media
• •
transmission media with some form of conductor that provides a conduit in which electromagnetic signals are contained •
•
it transports signals using electric current
a guided transmission medium and can be any physical facility used to propagate electromagnetic signals between two locations in a communication system •
30
guided unguided
Guided transmission media
Copper Cable transmission medium
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
•
include open wire, twin lead and pair copper wire as well as coaxial cable
twisted-
Metallic medium
transmission
•
the most common means of interconnecting devices in local area networks transmission of digital signals
Cable transmission medium
a metallic conductor system used to transfer energy from one point to another using electrical current flow; two or more electrical conductors separated by a nonconductive insulator (dielectric); can be as short as a few inches or span several thousand miles; can be used to propagate dc or lowfrequency ac or to propagate very high frequencies
Transmission lines
•
the displacement (amplitude) is in the direction of Longitudinal waves propagation; surface wave of water •
the direction of propagation of displacement is perpendicular to the direction of propagation; electromagnetic •
propagation of electrical power transmission line occurs in the ______________________ •
along form
Transverse waves
a Transverse electromagnetic of (TEM) waves
the E and H fields are perpendicular to each other (at 90° angles) at all points
Space quadrature
electromagnetic waves that travel along transmission line from the source to the load
Incident waves
•
•
a
•
those that travel from the load back toward the source
Reflected waves
it travel at approximately 1100 feet per second in the normal atmosphere
Sound waves
•
•
the rate at which the periodic wave repeats
Frequency
•
the distance of one cycle occurring in space
Wavelength
•
with two-wire balanced lines, both conductors carry current; however, one conductor carries the signal, and the other conductor is the return path
Differential or Balanced signal transmission
currents that flow in opposite directions in a balanced wire pair
Metallic circuit currents
•
•
Longitudinal currents
currents that flow in the same direction
31
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA •
Common mode rejection
cancellation of common mode signals
•
with an unbalanced transmission line, one wire is at ground potential, whereas the wire is at signal potential
Single-ended or Unbalanced signal transmission
•
a circuit device used to connect a balanced transmission line to an unbalanced load
Balun (balanced unbalanced)
•
are comprised of two or more metallic conductors separated by a nonconductive insulating material called a dielectric
Parallel-wire lines
transmission
•
two-wire parallel conductors; consist simply of two parallel wires, closely spaced and separated by air; its advantage is its simple construction; there is no shielding, radiation losses are high, and the cable is susceptible to picking up signals through mutual induction
Open-wire lines
transmission
occurs when a signal on one cable interferes with a signal on an adjacent cable
Crosstalk
•
•
it is called if the sleeve is woven into a mesh
Braid
•
it is given in dB of loss per 100 meters of cable with respect to frequency
Attenuation
•
given in dB of attenuation between the transmit signal and the signal is returned due to crosstalk with higher dB values indicating less crosstalk
Crosstalk
•
the name given to the area between the ceiling and the roof in a single building or between the ceiling and the floor of the next higher level in a multistory building
Plenum
•
plenum cables that coated with Teflon, which does not emit noxious chemicals when ignited, or special fire-resistant PVC
Plenum-grade PVC
•
a coaxial cable with one layer of foil insulation and one layer of braided shielding
Dual shielded
•
consist of two layers of foil insulation and two layers of braided metal shielding
Quad shielding
•
cables that are relatively expensive to manufacture and to minimize losses, the air insulator must be relatively free of moisture
Rigid-air filled coaxial
have lower losses than hollow cables and are easier to construct, install and maintain
Solid coaxial cables
•
32
to
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
sometimes referred to as “bayonet mount” as they can be easily twisted on or off •
•
are threaded and must be screwed on and off
BNC connectors
n-type connectors
•
the transmission characteristics of a transmission line
Secondary constants
•
defined as the impedance seen looking into an infinitely long line or the impedance seen looking into a finite length of line that is terminated in a purely resistive load with a resistance equal to the characteristic impedance of the line
Characteristic impedance (surge impedance)
used to express the attenuation (signal loss) and the phase shift per unit length of a transmission line
Propagation constant (propagation coefficient)
•
factor defined simply as the ratio of the actual velocity of Velocity propagation of an electromagnetic wave through a constant) given medium to the velocity of propagation through a vacuum (free space) •
•
1.0006
the relative dielectric constant of air
•
transmission lines designed to intentionally introduce a time delay in the path of an electromagnetic wave
Delay lines
•
a phenomenon that when current flows through an isolated round wire, the magnetic flux associated with it is in the form of concentric circles surrounding the wire core
Skin effect
•
the ratio of the ac resistance to the dc resistance of a conductor
Resistance ratio
•
it caused a difference of potential between two conductors of metallic transmission line
Dielectric heating
the energy radiated if the separation between conductors in a metallic transmission is an appreciable fraction of a wavelength, the electrostatic and electromagnetic fields that surround the conductor cause the line to act as if it were an antenna and transfer energy to a nearby conductive material
Radiation loss
•
it occurs whenever a connection is made to or Coupling loss from a transmission line or when two sections of transmission line are connected together •
33
(velocity
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
•
a luminous discharge that occurs between the two conductors of a transmission line when the difference of potential between them exceeds the breakdown voltage of the dielectric insulator
Corona
•
voltage that propagates from the source toward the load
Incident voltage
voltage that propagates from the load toward the source
Reflected voltage
•
•
Flat or nonresonant line
a transmission line with no reflected power
•
defined as the ratio of the maximum voltage to the minimum voltage or the maximum current to the minimum current of a standing wave on a transmission lin
Standing Wave Ratio (SWR)
•
used to match transmission lines to purely resistive loads whose resistance is not equal to the characteristic impedance of the line
Quarter-wavelength
•
simply a piece of additional transmission line that is placed across the primary line as close to the load as possible; the susceptance is to tune out the susceptance of the load
Transmission-line stub
•
a technique that can be used to locate an impairment in a metallic cable
Time-domain reflectometry (TDR)
•
simply a flat conductor separated from a ground plane by an insulating dielectric material
Microstrip
simply a flat conductor sandwiched between two ground planes; less likely to radiate; losses are lower
Stripline
•
CHAPTER 13 : Optical Fiber transmission Media the bandwidth of an analog communications system is expressed as a percentage of its carrier frequency • it was a device constructed from mirrors and •
34
Bandwidth utilizations ratio
Photophone
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
selenium detectors that transmitted sound waves over a beam of light he successfully transmitted images through a single glass fiber •
they experimented with through bundles of fibers •
light
H. Lamm
transmission
• • •
it was when the three scientists experimented on a bundle of glass fiber the transmission of light •
•
A.C.S van Heel H.H. Hopkins N.S. Kapany
1951
N.S. Kapany
he coined the term fiber optics
Charles H. Townes Arthur L. Schawlow
they wrote a paper describing how it was possible to use stimulated emission for amplifying light waves as well as microwaves
•
defined as the maximum angle in which external light rays may strike the air/glass interface and still propagate down the fiber
Acceptance angle
•
•
•
•
Acceptance cone half-angle
other term used for acceptance angle
closely related to acceptance angle and is figure of merit commonly used to measure the magnitude of the acceptance angle •
Numerical aperture
•
the refractive index of a glass core
1.5
•
only one path for light rays to take down a cable
Single mode
•
more than one path
Multimode
the term that means path in fiber optics technology
Mode
these parameters propagates
•
•
•
dictate
how
a
light
•
mode or propagation index profile of fiber
•
the graphical representation of the magnitude of the refractive index across the fiber
Index profile
•
has a central core with a uniform refractive index
Step-index fiber
•
no cladding and the refractive index of the core is nonuniform
Graded-index fiber
has a central core that is smaller in diameter that any of the multimode cables
Single-mode step-index fiber
•
35
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
type of fiber has a large light to fiber aperture and allows more external light to enter the cable •
Multimode step-index optical fiber
•
the light rays that make up the pulse spread out in time, causing a corresponding reduction in the pulse amplitude and stretching of pulse width
Pulse spreading
•
other term used for pulse spreading
Pulse-width dispersion
•
UPRZ is the acronym for _____
Unipolar return to zero
•
a condition wherein the energy from pulse a were to fall back one-half of a bit time, it would interfere with pulse b
UPNRZ transmission
•
UPNRZ is the acronym for _____
Unipolar nonreturn to zero
•
the light energy from pulse a were to fall back one bit time, it would interfere with pulse b and change what was a logic 0 to logic 1
UPRZ
•
the difference between the absolute delay times of Pulse spreading constant the fastest and slowest rays of light propagating down a fiber of unit length
•
equal to the pulse spreading constant times the total fiber length
Total pulse spread
•
caused by imperfect physical connections
Coupling losses
•
the other term used for gap displacement
End separation
•
the typical value of displacement less than 2
•
these are the spectral widths of a standard LED
30 nm to 50 nm
•
the wavelength equivalent of bandwidth
Linewidth
•
a pn junction diode usually made from a semiconductor material such as aluminum gallium arsenide or gallium arsenide phosphide
LED
•
a group iv atom used to produce light wavelengths in the 800 nm range
Arsenide
•
a small batterylike device that produced a dc output voltage proportional to the amount of light received
Photocell
•
a special high-intensity, single frequency light source. it produces a very narrow beam of brilliant
Laser
loss
for
an
angular
36
Less 0.5 dB
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
light of a specific wavelength (color); it can penetrate atmospheric obstacles better than other type of light, •
commonly used as a light source, this is a semiconductor device that puts out a low-intensity red light beam
LED
•
another commonly used light source, that generates an extremely intense single frequency light beam
Solid-state laser
•
light sensitive device, used to detect the light pulses; converts the light pulses to electrical signal
Photocell or light detector
CHAPTER 14: Electromagnetic Wave Propagation •
a form of electromagnetic radiation that consist of traveling electric and magnetic fields
Radio waves
orientation of the electric field vector in respect to the surface of earth
Polarization
•
•
Linear polarization
the polarization remains constant
•
a form of linear polarization when the electric field is propagating parallel to the Earth’s surface
Horizontal polarization
if the electric field is propagating perpendicular to the Earth’s surface
Vertical polarization
•
if the polarization vector rotates 360° as the Circular polarization wave moves one wavelength through the space and the field strength is equal at all angles of polarization • when the field strength varies with changes in Elliptical polarization polarization •
shows a surface of constant phase of Wavefront electromagnetic waves; formed when points of equal phase on rays propagated from the same source are joined together •
•
a single location from which rays propagate equally in all directions
Point source
an invisible force field produced by a magnet, such as a conductor when current is flowing through it
Magnetic field
•
37
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
•
the rate at which energy passes through a given surface area in free space
Power density
•
also an invisible force fields produced by a difference in voltage potential between two conductors
Electric fields
•
a source that radiates power at a constant rate uniformly in all directions
Isotropic radiator
•
the power density is inversely proportional to the square of the distance from the source
Inverse square law
•
reduction in power density and occurs in free space as well as the Earth’s atmosphere
Attenuation
•
the reduction of power where in it contains particles that can absorb electromagnetic energy
Absorption loss
•
the reduction in power density due to nonfreespace propagation
Absorption
•
sometimes referred to as the bending of the radio-wave path
Refraction
•
the angle formed between the incident wave and the normal
Angle of incidence
•
the angle formed between the refracted wave and the normal
Angle of refraction
•
the ratio of the velocity of propagation of a light ray in free space to the velocity of propagation of a light ray in a given material
Refractive index
•
the ratio of the reflected to the incident voltage intensities
Reflection coefficient
a condition when an incident wavefront strikes an irregular surface, it randomly scattered in many directions
Diffuse reflection
•
•
reflection from a perfectly smooth surface
the fraction of power that penetrates medium two •
•
Specular reflection
Absorption coefficient
states that a semirough surface will reflect as if it were a smooth surface whenever the cosine of Rayleigh criterion the angle of incidence is greater than λ /8d , where d is the depth of the surface irregularity and λ is the wavelngth of the incident wave 38
(mirrorlike)
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
defined as the modulation or redistribution of Diffraction energy within a wavefront when it passes near the edge of an opaque object; the phenomenon that allows light or radio waves to propagate around corners •
•
states that every point on a given spherical wavefront can be considered as a secondary point source of electromagnetic waves from which other secondary waves are radiated outward
Huygen’s principle
•
occurs whenever two or more waves simultaneously occupy the same point in space; states that the total voltage intensity at a given point in space is the sum of the individual wave sectors
Linear superposition
•
electromagnetic waves traveling within Earth’s atmosphere
Terrestrial waves
communications between two or more points on Earth
Terrestrial communications
•
•
direct and ground-reflected waves together
Space waves
•
the cumulative sum of the direct, groundreflected, and surface waves
Ground wave
•
depends on the presence of the ionized layers above the Earth that return some of the energy that otherwise would be lost in outer space
Sky wave
•
an earth-guided electromagnetic wave that travels over the surface of Earth;
Surface waves
•
travel essentially in a straight line between the transmit and received antennas
Direct waves
•
occurs when the density of the lower atmosphere is such that electromagnetic waves are trapped between it and Earth’s surface
Duct propagation
electromagnetic waves that are directed above the horizon
Sky waves
•
•
Ionospheric propagation
another term for sky wave propagation
•
the lowest layer of the ionosphere and is located approximately between 30 miles and 60 miles above Earth’s surface
D layer
•
E layer
located approximately between 60 miles and 85 miles above the Earth’s surface; sometimes called Kennelly-Heavyside layer 39
radio
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
•
made up of two layers F 1 and F2 layers; during daytime, F1 layer is located between 85 miles and 155 miles above the earth’s surface; the F 2 layer is located 85 miles to 185 miles above the Earth’s surface during winter and 155 miles to 220 miles in the summer
F layer
•
defined as the highest frequency that can be propagated directly upward and still be returned to earth by the ionosphere; depends on the ionization density and, therefore varies with the time of day and season
Critical frequency (f c)
•
the height above earth’s surface from which a refracted wave appears to have been reflected
Virtual height
•
the highest frequency that can be used for sky wave propagation between two specific points on Earth’s surface
Maximum (MUF)
•
a law that assumes a flat Earth and a flat reflecting layer can never exist
Secant law
•
85% of the MUF that provides more reliable communications
Optimum working frequency (OWF)
defined as the minimum distance from a transmit antenna that a sky wave at a given frequency will be returned to Earth usually of little significance, as it tends to be • much weaker than the lower ray because it spreads over a much larger area than the lower ray
Skip distance
•
the area between where the surface waves are completely dissipated and the point where the first sky wave returns to Earth
Quiet or skip zone
often defined as the loss incurred by an electromagnetic wave as it propagates in a straight line through a vacuum with no absorption or reflection of energy from nearby objects it occurs simply because of the inverse square • law
Free-space path loss
•
loss attributed to several different phenomena and can include both short- and long- term
Fading
an additional loss is added to the normal path loss to accommodate temporary fading
Fade margin
•
•
•
40
usable
frequency
Pedersen ray
Spreading loss
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
CHAPTER 15 : Antennas and Waveguide the plane parallel to the mutually perpendicular lines of the electric and magnetic fields •
•
Radiation efficiency
the ratio of radiate to reflected energy
antenna wherein the conductors are spread out in a straight line to a total length of one-quarter wavelength •
•
Wavefront
Quarter-wave antenna (vertical monopole sometimes called Marconi antenna ) Hertz antenna
a half wave dipole
•
meaning two dipoles that is used to radiate more energy by simply spreading the conductors farther apart
Dipole
•
a basic antenna that cannot amplify a signal, at least not in the true sense of the word
Passive reciprocal device
•
a special coupling device that can be used to direct the transmit and receive signals and provide the necessary isolation
Diplexer
a polar diagram or graph representing field strength or power densities at various angular positions relative to an antenna
Radiation pattern
•
primary beam in a 90° direction
Major lobe
•
represent undesired radiation or reception
Minor lobe
•
the lobe that receives the most energy
Front lobe
•
•
lobes adjacent to the front lobe (the 180 ° minor lobe)
Side lobes
•
lobes in a direction exactly opposite the front lobe
Back lobe
ratio of the front lobe power to the back lobe power
Front-to-back ratio
•
•
Front-to-side ratio
the ratio of the front lobe to a side lobe
the line bisecting the major lobe, or pointing Line of shoot (point of shoot) from the center of the antenna in the direction of maximum radiation •
•
refers to the filed that is close to the antenna
41
Near field
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
refers to the field pattern that is at great distance •
•
Far field
Induction field
sometimes called to near field
sometimes called for far field because power that reaches the far field continues to radiate outward and is never returned to the antenna an ac antenna resistance and is equal to the • ratio of the power radiated by the antenna to the square of the current at its feedpoint
Radiation field
the ratio of the power radiated by an antenna to the sum of the power radiated and the power dissipated or the ratio of the power radiated by the antenna to the total input power
Antenna efficiency
•
•
Radiation resistance
the ratio of the power density radiated in a Directive gain particular direction to the power density radiated to the same point by a reference antenna, assuming both antennas are radiating the same amount of power •
•
Directivity
the maximum directive gain
•
the same as directive gain except that the total power fed to the antenna is used; it is assumed that the given antenna and the reference antenna is lossless
Power gain
•
defined as an equivalent transmit power; the equivalent power that an isotropic antenna would have to radiate to achieve the same power density in the chosen direction at a given point as another antenna
Effective Isotropic Power (EIRP)
•
the power density in space and a somewhat misleading quantity
Captured power density
•
refers simply to the orientation of the electric field radiated from it.
Polarization of an antenna
•
simply the angular separation between the two half-power points on the major lobe of an antenna’s plane radiation pattern, usually taken in one of the “principal” planes
Beamwidth
•
vaguely defined as the frequency range over which antenna operation is “satisfactory”
Antenna bandwidth
normally taken as the difference between the half-power frequencies but sometimes refers to variations in the antenna’s input impedance
Bandwidth
•
42
Radiated
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
the point on the antenna where the transmission line is connected • the feedpoint presents an ac load to the transmission line •
•
Feedpoint Antenna input impedance
Elementary doublet
an electrically short dipole
•
a multiple of quarter-wavelength long and open circuited at the far end
Resonant antenna
•
a monopole antenna one-quarter wavelength long, mounted vertically with the lower end either connected to ground or grounded through the antenna coupling network
Marconi antenna
•
a wire structure placed below the antenna and erected above the ground; should be insulated from earth ground
Counterpoise
•
a technique wherein the physical length of an antenna remains unchanged although its effective electrical length is increased
Loading
•
a coil (inductor) added in series with a dipole antenna that effectively increases the antenna’s electrical length
Loading coil
•
a technique where in a metallic array that resembles a spoked wheel is placed on top of the antenna
Top loading
•
formed when two or more antenna elements are combined to form a single antenna
Antenna array
•
an individual radiator, such as a half- or quarterwave dipole
Antenna element
•
elements that are directly connected to the transmission line and receive power from or are driven by source
Driven elements
•
not connected to the transmission line; they receive energy only through mutual induction with a driven element or another parasitic element
Parasitic element
•
a parasitic element that is longer than the driven element from which it receives energy; effectively reduces the signal strength in its direction and increases it in the opposite direction
Reflector
a parasitic element that is shorter than its associated driven element; increases field strength in its direction and reduces it in the opposite direction
Director
•
43
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
one of the simplest types of antenna rays; made Broadside array by simply placing a several resonant dipoles of equal size in parallel with each other and in a straight line •
essentially the same element configuration as End-fire array the broadside array except that the transmission line is not crisscrossed between elements; as a result the field are additive in line with the plane of the array •
a nonresonant antenna that is capable of Rhombic antenna operating satisfactorily over a relatively wide bandwidth making it ideally suited for HF transmission •
essentially a single antenna made up of two elements •
•
Folded dipole
Fat dipole
dipole elements larger in diameter;
antenna named after two Japanese scientists Yagi-uda antenna who invented it and describe its operation •
a linear array consisting of a dipole and two or Yagi antenna more parasitic elements: one reflector and one or more directors •
•
formed by placing two dipoles at right angles to each other 90° out of phase
Turnsile antenna
•
a class of frequency-independent antennas where in its primary advantage is the independence of their radiation and radiation pattern to frequency; from the initial work of V. H. Rumsey, J. D. Dyson, R. H. DuHamel and D.E. Isbell
Log-periodic antennas
•
the ratio of the highest to the lowest frequency over which antenna will satisfactorily operate
Bandwidth ratio
•
simply a single-turn coil of wire that is significantly shorter than one wavelength and carries RF current
Loop antenna
a group of antenna or a group of antenna arrays that, when connected together function as a single antenna whose beamwidth and direction can be changed electronically without having to physically move any of the individual antennas or antenna elements within the array
Phased array antenna
•
44
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
•
a broadband VHF or UHF antenna that is ideally suited for applications for which radiating circular rather than horizontal or vertical polarized electromagnetic waves; used as a single element antenna or stacked horizontally or vertically in an array to modify its radiation pattern by increasing the gain and decreasing the beamwidth of the primary lobe
Helical antenna
•
electromagnetic radiation is in a direction at right angles to the axis of the helix
Normal mode
•
radiation is in the axial direction and produces a broadband, relatively directional pattern
Axial mode
defined as the ratio of its maximum gain in the forward direction to its maximum gain in its backward direction
Front-to-back ratio
•
used with point-to-point microwave systems
Highly directional antennas
provide extremely high gain and directivity and are very popular for microwave radio and satellite communications skills
Parabolic reflector antennas
•
•
•
two main parts of parabolic antenna:
• •
parabolic reflector feed mechanism
resemble the shape of a plate or dish; a plane Parabolic reflectors dish, curve that is defined as the locus of a point that (parabolic antennas) moves so that its distance from another point added to its distance from a straight line is of constant length •
the ratio of the focal length to the diameter of Aperture ratio the mouth of the parabola •
•
Paraboloid
the resulting curved surface dish
energy near the edge of the dish does not Spillover or leakage reflect but rather is diffracted around the edge of the dish •
•
considers both the radiation pattern of the primary radiator and the effect
Aperture efficiency
•
the ratio of the focal length of the antenna to the reflector diamtere
Aperture number
houses the primary antenna which radiates electromagnetic waves toward the reflector
Feed mechanism
•
45
dish
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
three primary types of feed mechanism for parabolic antennas: •
• • •
•
the primary antenna is placed at the focus
center feed horn feed cassegrain feed
Center feed
•
the primary antenna is a small horn antenna rather than a simple dipole or dipole array
Horn feed
the primary radiating source is located in or just behind a small opening at the vertex of the paraboloid rather than at the focus
Cassegrein feed
•
consists of a cone that is truncated in a pice of Conical horn antenna circular waveguide; the waveguide in turn connects the antenna to either the transmitter or the receiver •
•
a hollow conductive tube, usually rectangular in cross section but sometimes circular or elliptical
Waveguides
•
the velocity at which a wave propagates; the velocity at which information signals of any kind are propagated; also the velocity at which energy is propagated; can be measured by determining the time it takes for a pulse to propagate a given length of a waveguide
Group velocity
velocity at which the wave changes phase; the apparent velocity of a particular phase of the wave; the velocity with which a wave changes phase in a direction parallel to a conducting surface; such as the walls of a waveguide
Phase velocity
•
minimum frequency of operation; the absolute Cutoff frequency limiting frequency; frequencies above the cutoff frequency will not be propagated by the waveguide •
•
maximum wavelength that they can propagate; defined as the smallest free-space wavelength that is just unable to propagate in the waveguide
Cutoff wavelength
•
the travel of electromagnetic waves down a waveguide in different configurations
Propagation of modes
•
means that the electric field lines are everywhere transverse (perpendicular to the guide walls)
TE
waveguides used in radar and microwave applications when it is necessary or advantageous to propagate both vertically and horizontally
Circular waveguide
•
46
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
polarized waves in the same waveguide •
waveguide that is more expensive to manufacture than a standard rectangular waveguide; however it allows operation at lower frequencies for a given size
Ridged waveguide
consists of a spiral-wound ribbons of brass or copper; used extensively in microwave test equipment
Flexible waveguide
•
CHAPTER 16: Telephone Instruments and Signal •
a part of global communications network which uses telephone or a data modem on a telephone network
Public (PTN)
PTN that interconnects subscribers through one or more switches
Public switch network (PSTN)
•
telephone
network
telephone
the simplest and most straightforward form of Plain old telephone service telephone service which involves subscribers (POTS) accessing the public telephone network through a pair of wires •
simply an unshielded twisted-pair transmission Subscriber loop (local loop) line (cable pair) consisting of two insulated conductors twisted together; generally comprised of several lengths of copper wire interconnected at junction and cross-connect boxes located in manholes, back alleys, or telephone equipment rooms with large buildings and building complexes •
•
means to connect a telephone set at a subscriber’s location to the closest telephone office, which is commonly called an end office, local exchange office, or central office
Subscriber loop
•
enables the subscriber to access the public telephone network
Electronic (ESS)
the quality of transmission over a telephone depends on:
•
•
•
•
•
helps prevent the speaker from talking too 47
switching
system
received volume relative frequency response of the telephone circuit degree of interference
Sidetone/talkback
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
loudly •
pair of wires connecting a subscriber to the closest telephone office
Local loop
•
one wire on the local loop come from the ¼-inch-diameter two-conductor • phone plugs and patch cords used at telephone company switch-boards to interconnect and test circuits
Tip Tip and Ring
•
standards for registered jacks and is sometimes called as RJ-XX; a series of telephone connection interfaces (receptacle and plug) that are registered with the U.S. FCC
RJ
•
the most common telephone jack in use today and can have up to six conductors
RJ-11
reasons why a dc voltage was used rather than an ac voltage
•
•
•
•
voltage selected to minimize electrolytic corrosion on the loop wires; used for supervisory signaling and to provide talk battery for the microphone in the telephone set •
•
examples of supervisory signals
prevent power supply hum allow service to continue in the event of a power outage people were afraid of ac
-48 Vdc
• • •
on-hook off-hook dial pulsing
•
placed directly across the tip and ring of the local loop; the purpose of the ringer is to alert the destination party of incoming calls
Ringer circuit
•
a simple single-throw, double pole (STDP) switch placed across the tip and ring; mechanically connected to the telephone is idle (on hook) is open; when the telephone is in use (off hook) is closed completing an electrical path through the microphone between the tip and ring of the local loop
On/off hook circuit (switch)
•
combinations of passive components that are used to regulate the amplitude and frequency response of the voice signals
Equalizer
•
Speaker
the receiver for the telephone; converts electrical signals received from the local loop to 48
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
acoustical signals (sound waves) that can be heard and understood by a human being; connected to the local loop through the hybrid network; typically enclosed in the handset of the telephone along with the microphone •
the transmitter for the telephone; converts acoustical signals in the form of sound pressure waves from the caller to electrical signals that are transmitted into the telephone network through the local subscriber loop
Microphone
•
a special balanced transformer used to convert a two-wire circuit (the local loop) into a four-wire circuit (the telephone set) and vice versa, thus enabling full duplex operation over a two-wire circuit
Hybrid network (hybrid coil or duplex coil)
•
enables the subscriber to output signals representing digits and this enables the caller to enter the destination telephone number; either an electronic dial-pulsing circuit or a Touch-Tone keypad which sends various combinations of tones representing the called digits
Dialing circuit
•
are acknowledgement and status signals that ensure the processes necessary to set up and terminate a telephone call are completed in an orderly and timely manner
Call progress tones and call progress signals
•
the exchange of signaling messages over local loops between stations (telephone) and telephone company switching machines
Station signaling
the exchange of signaling messages between switching machines
Interoffice signaling
•
indicate a request for service such as going off Alerting signals hook or ringing the destination telephone •
provide call status information, such as busy or ring-back signals •
provide information in the form announcements such as number changed another number, a number no longer in service •
of Controlling signals to
provide the routing information such as calling and called numbers •
Supervising signals
Addressing signals
Call Progress Tone Summary Tone or
Frequency
49
Duration/Range
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
Signal Dial tone DTMF
350 Hz plus 440 Hz 697 Hz, 770 Hz, 852 Hz, 941 Hz, 1209 Hz, 1336 Hz, 1477 Hz, 1633 Hz
MF
700 Hz, 900 Hz, 1100 Hz, 1300 Hz, 1500 Hz, 1700 Hz
Dial pulses
Open/closed switch
Station busy
480 Hz plus 620 Hz
Equipment busy Ringing
480 Hz plus 620 Hz 20 Hz, 90 vrms (nominal)
Ring-back
440 Hz plus 480 Hz
Receiver on hook Receiver off hook Receiver-leftoffhook alert
Open loop Dc current 1440 Hz, 2060 Hz, 2450 Hz, 2600 Hz
a 2600-Hz frequency tone placed on a circuit to indicate the circuit is not currently in use •
Continuous Two of eight tones On, 50-ms minimum Off, 45-ms minimum 3-s minimum Two of six tones On, 90-ms minimum 120-ms maximum On, 39 ms Off, 61 ms On, 0.5 s Off, 0.5 s On, 0.2 s Off, 0.3 s On, 2 s Off, 4 s On, 2 s Off, 4 s Indefinite 20 mA minimum 80 mA maximum On, 0.1 s Off, 0.1 s
IDLE signal
a multifrequency control tone comprised of Key Pulse (KP) signal 1100 Hz plus 1700 Hz ranging from 90 ms to 120 ms; used to indicate the beginning of a sequence of MF digits •
pulsing the method originally used to transfer digits Dial pulsing) from a telephone set to the local switch •
(rotary
dial
is sent from the switching machine back to the Station busy signal calling station whenever the called telephone number is off hook; a two-tone signal comprised of 480Hz and 620 Hz •
•
sent from the switching machine back to the 50
Equipment
busy
signal
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
calling station complete the unavailability
whenever the call because
system cannot of equipment
(congestion available)
tone/no-circuits-
•
whenever the system is overloaded and more calls are being placed than can be completed
Blocking
•
sent from a central office to a subscriber whenever there is an incoming call; the purpose is to ring the bell in the telephone set to alert the subscriber that there is an incoming call
Ringing signal
•
sent back to the calling party at the same time the ringing signal is sent to the called party; the purpose is to give some assurance to the calling party that the destination telephone number has been accepted, processed, and is being rung
Ring-back signal
•
simply tones that operate cords attached to the handset; a full duplex, battery-operated , portable radio transceiver that communicates directly with a stationary transceiver located somewhere in the subscriber’s office
Cordless telephone
•
enables the destination of a telephone call to display the name and telephone number of the calling party before the telephone is answered; allows subscribers to screen incoming calls and decide whether they want to answer the telephone; a simplex transmission sent from the central office switch over the local loop to a caller ID display unit at the destination
Caller ID
simplex wireless communications system deigned to alert subscribers of awaiting messages; relay radio signals and messages from wire-line and cellular telephones to subscribers carrying portable receivers
Paging transmitters
•
CHAPTER 17 : The Telephone Circuit •
the network bandwidth for a standard voiceband message channel
4 kHz
the only facility required by all voice-band circuits, as it is the means by which subscriber locations are connected to the local telephone company
Local subscriber loop
•
51
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
a metallic transmission line comprised of two insulated copper wires (a pair) twisted together •
•
Local loop
Attenuation
an actual loss of signal strength
•
occurs when two or more frequencies undergo different amounts of phase shift
Phase distortions
depend on the wire diameter, conductor spacing, dielectric constant of the insulator separating the wires and the conductivity of the wire refers to the electrical characteristics of a cable • uniformly distributed along its length
Transmission characteristics
•
the largest cable used in a local loop, usually 3600 pair of copper wire placed underground or in conduit
Feeder cable (F1)
•
a cross-connect point used to distribute the larger feeder cable into smaller distribution cables
Serving area interface (SAI)
•
a smaller version of a feeder cable containing less wire pairs
Distribution cable (F2)
•
a device that serves as the demarcation point between local telephone company responsibility and subscriber responsibility for telephone service
Subscriber or standard network interface (SNI)
•
the final length of cable pair that terminates at the SNI
Drop wire
•
that portion of the local loop that is strung between poles
Aerial
•
the location where individual cable pairs within a distribution cable are separated and extended to the subscriber’s location on a drop wire
Distribution cable and dropwire cross-connect point
•
an irregularity found in cables serving subscriber locations; unused sections of cable that are connected in shunt to a working cable pair
Bridge tap
•
the basic yardstick used for making power measurements in communications
Decibel, dB
•
defined as the optimum level of a test tone on a channel on a channel at some point in a communications system
Transmission (TLP)
the ratio in dB of the power of a signal at that point to the power the same signal would be at a 0dBm transmission level point
Transmission level (TL)
•
•
52
Distributed parameters
level
point
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
•
a parameter used as a reference for data transmission
Data level point (DLP)
•
used primarily in Europe; assumes a perfect receiver; therefore, its weighting curve corresponds to the frequency response of the human ear only
Psophometric noise weighting
apply to dedicated private-line data circuits that utilize the private sector of the public telephone network – circuits with bandwidths comparable to those of standard voice-grade telephone channels that do not utilize the public switched telephone network
Transmission parameters
direct locations
Private-line circuits
•
•
connections
between
two
or
more
the difference in circuit gain of a reference frequency •
an indirect method of evaluating the phase delay characteristics of a circuit •
Attenuation distortion (frequency response, differential gain and 1004-Hz deviation) Envelope delay distortion
the process used to improve a basic telephone channel; improves the high frequency response of a message channel and reduces power loss • specifies the maximum limits for attenuation and envelope delay distortion; pertains to line impairments for which compensation can be made with filters and equalizers
Line conditioning
•
telephone systems provided by local telephone companies dedicated to a single customer, usually with a large number of stations
Private switched networks
a relatively low-capacity switching machine where the subscribers are generally limited to stations within the same building or building complex • the time delay encountered by a signal as it propagates from a source to a destination
Private (PBX)
•
delay measured in angular units, such as degrees or radians
Phase delay
•
the actual time required for a particular frequency to propagate from a source to a destination through a communications channel
Absolute phase delay
evaluate not the true phase-versus-frequency characteristics but rather the phase of a wave that is the result of a narrow band of frequencies
Envelope delay
•
•
•
53
C-type conditioning
branch
exchange
Propagation time
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
•
the phase difference at the different carrier frequencies; indicates the relative delays of the various carrier frequencies with respect to the reference frequency
Envelope delay distortion
neither reduces the noise on a circuit nor improves the signal-to-noise ratio; a requirement and does not add anything to the circuit and it cannot be used to improve a circuit; it simply places higher requirements on circuits used for high-speed data transmission
D-type conditioning
unwanted frequencies
Harmonic distortion
•
•
multiples
of
the
transmitted
•
cross products [sums and differences] of the transmitted frequencies
Intermodulation distortion (fluctuation noise or crossmodulation noise)
•
the purpose is to simulate the combined signal power of a standard voice-band data transmission
1004-Hz test tone
•
determine the average weighted rms noise power
C-message noise
•
differ from standard C-message noise measurements only in the fact that a holding tone is applied to the transmit end of the circuit while the noise measurement is taken
C-notched noise
•
ensures that the circuit operation simulates a loaded voice or data transmission
Holding current
a communications term that indicates the presence of a signal power comparable to the power of an actual message transmission
Loaded
•
characterized by high-amplitude peaks Impulse noise (impulses) of short duration having an approximately flat frequency spectrum; can saturate a message channel; the primary source of transmission errors in data circuits •
a sudden, random change in the gain of a circuit resulting in a temporary change in the signal level •
Gain hit
a decrease in circuit gain of more than 12 dB Dropout lasting longer than 4 ms; characteristics of temporary open-circuit conditions and are generally caused by deep fades on radio facilities or by switching delays •
54
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA •
sudden, random changes in the phase of a signal; are classified as temporary variations in the phase of a signal lasting longer than 4 ms
Phase hits (slips)
•
a form of incidental phase modulation-a continuous, uncontrolled variation in the zero crossings of a signal; occurs at a 300 Hz rate or lower and its primary cause is low-frequency ac ripple in power supplies
Phase jitter
•
the presence of one or more continuous, unwanted tones within a message channel
Single-frequency interference
unwanted tones caused by crosstalk or cross modulation between adjacent channels in a transmission system due to system nonlinearities occurs in coherent SSBSC systems, such as • those using frequency-division multiplexing when the received carrier is not reinserted with the exact phase relationship to the received signal as the transmit carrier possessed
Spurious tones
•
used to match impedances and to provide isolation between the two directions of signal flow
Hybrid set
•
used to convert two-wire circuits to four-wire circuits similar to the hybrid coil found in standard telephone sets
Hybrid circuits
eliminate the echo electrically subtracting it from the original signal rather than disabling the amplifier in the return circuit
Echo cancellers
•
•
•
Phase intercept distortion
Echo suppressors
used to eliminate echo
can be defined as any disturbance created in a communications channel by signals in other communications channels; a potential problem whenever two metallic conductors carrying different signals are located in close proximity to each other; was originally coined to indicate the presence of unwanted speech sounds in a telephone receiver caused by conversations on another telephone circuit •
Crosstalk
crosstalk cause by inadequate control of the Transmittance crosstalk transfer characteristics or transmittance of networks •
electromagnetic coupling between two or more physically isolated transmission media; •
•
crosstalk that occurs at the transmit end of a
55
Coupling crosstalk
Near-end crosstalk (NEXT)
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
circuit and travels in the opposite direction as the signal in the disturbing channel •
occurs at the far-end receiver and is energy that travels in the same direction as the signal in the disturbing channel
Far-end crosstalk (FEXT)
referenced to the level on the cable that is being interfered with
dBx for crosstalk
•
CHAPTER 18 : The Public Telephone Network •
identifies and connects the subscribers to a suitable transmission path
Switching functions
•
supply and interpret control and supervisory signals needed to perform the operation
Signaling functions
•
involves the actual transmission system of a subscriber’s messages and any necessary control signals
Transmission functions
•
referred to the leased lines designed and configured for their use only
Private-line (dedicated lines)
equipment and facilities that are available to all the public subscribers to the network which includes transmission facilities and telephone switches
Common usage equipment
sometimes companies
Service providers
•
•
called
to
public
telephone
•
simply the dedicated facility used to connect an instrument at a subscriber’s station to the closest telephone office
Local loop
•
similar to local loop except trunk circuits used to interconnect two telephone offices; a common usage connection; can be simple as a pair of copper wires twisted together or as sophisticated as an optical fiber cable
Trunk circuit
allows any telephone connected to it to be interconnected to any of the other telephones connected to the exchange without requiring separate cable pairs and telephones for each connection
Telephone exchange
•
56
circuits
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA •
the first telephone exchanges where manual interconnects were accomplished using patchcords and jacks
Switchboards
•
each telephone line that could have 10 or more subscribers connected to the central office exchange using the same loop
Party line
•
a programmable matrix that allows circuits to be connected to one another; interconnect input loop or trunk circuits to output loop or trunk circuits
Circuit switch
•
local exchanges centrally located within the area they serve; can directly interconnect any two subscribers whose local loops are connected to the same local exchange
Central offices (CO)
•
a telephone call completed within a single local exchange
Intraoffice call)
•
calls placed between two stations that are connected to different local exchanges
Interoffice calls
an exchange without any local loops connected to it
Tandem office
•
call
(intraswitch
•
called switcher’s switch
Tandem switch
•
trunk circuits that terminate in tandem switches
Tandem trunks (intermediate trunks)
•
was established to provide a telephone numbering system for the United States, Mexico, and Canada that would allow any subscriber in North America to direct dial virtually any other subscriber without the assistance of an operator
North American Telephone Numbering Plan (NANP)
•
allows many subscribers to share a limited number of lines to a central office switch
Concentrator
•
splits the two directions of signal propagation so that the actual long-distance segment of the route can be accomplished on a four-wire basis
Terminating set (hybrid)
•
allows a certain degree of route selection when establishing a telephone call
Switching hierarchy
simply a path between two subscribers and is comprised of one or more switches, two local loops, and possibly one or more trunk circuits
Route
•
•
an equipment busy signal received by the
57
Blocking
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
calling party if a call cannot be completed because the necessary trunks or circuits are not available a local exchange where subscriber loops terminated and received dial tone; end offices interconnected subscriber loop to other subscriber loops and subscriber loops to tandem trunks, interoffice trunks, and toll-connecting trunks •
•
Class 5 end office
Class 3 primary center
provided no operator assistance
•
provide service to geographical regions varying in size from part of a state to all of several states, depending on population density
Class 2 sectional center
•
the highest-ranking office in the DDD network in terms of the size of the geographical area serves and trunking options available
Class 1 regional center
a global standard for telecommunications defined by the International Telecommunications Union (ITU) Telecommunications Sector (ITU-T); was developed as an alternate and much improved means of transporting signaling information through the public telephone network;
Common channel no. 7 (SS7 or C7)
•
signaling
a telecommunications term that describes the Point-of-presence legal boundaries for the responsibility of maintaining equipment and transmission lines; a demarcation point separating two companies • allows customers to change to a different Porting service and still keep the same telephone number •
•
store information about subscriber’s services, routing of special service numbers and calling card validation for fraud protection and provide information necessary for advanced call-processing capabilities
Databases
provides access from one level of the protocol to another level
Primitive
•
CHAPTER 19 : Cellular Telephone Companies utilized frequency modulation and were generally assigned a single carrier frequency in the 35 MHz to 45 MHz range that was used by both the mobile unit and the base station •
58
Mobile telephone systems (MTSs) (manual telephone system)
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
•
small handsets, easily carried by a person in their pocket or purse
Mobile telephone stations
•
suggested any radio transmitter, receiver, or transceiver that could be moved while in operation
Mobile
•
described a relatively small radio unit that was handheld, battery powered, and easily carried by a person moving at walking speed
Portable
similar to two-way mobile radio in that most communications occurs between base stations and mobile units; best describe by pointing out the primary difference between it and two-way mobile radio
Cellular telephone
•
•
push-to-talk
PTT
•
examples of two-way mobile radio
• •
citizen’s band (CB) public land mobile radio
Evolution of Cellular Telephone July 28, 1945 : Saturday Evening Post, E. K. Jett , then the commissioner of the FCC hinted of a cellular telephone scheme that he referred to as simply s small zone radio telephone system June 17, 1946 : in St. Louis Missouri, AT&T and Southwestern Bell introduced the first American commercial mobile radio-telephone service to private customers. In the same year, similar services were offered to 25 major cities throughout the United States early 1950s : the FCC doubled the number of mobile telephone channels by reducing the bandwidth to 60 kHz per channel 1960 : AT&T introduced direct-dialing, full-duplex mobile telephone service with other performance enhancements 1966 : Don Adams, in a television show called Get Smart , unveiled the most famous mobile telephone to date: the fully mobile shoe phone 1968 : AT&T proposed the concept of cellular mobile system to the FCC with the intent of alleviating the problem of spectrum congestions in the existing mobile telephone system 1974 : the FCC allocated an additional 40-MHz bandwidth for cellular telephone service 1975 : the FCC granted AT&T the first license to operate a development cellular telephone service in Chicago 1976 : the Bell Mobile Phone service for metropolitan New York City offered only 12 channels that could serve a maximum of 543 subscribers. FCC granted authorization to the American Radio Telephone Service (ARTS) to install a second developmental system in the Baltimore- Washington, D.C., area 1983 59
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
: the FCC allocated 666 30 kHz half-duplex mobile telephone channels to AT&T to form the first U.S. cellular telephone system called Advanced Mobile Phone System (AMPS) 1991 : the first digital cellular services were introduced in several major U.S. cities, enabling a more efficient utilization of the available bandwidth using voice compression November 17, 1998 : a subsidiary of Motorola Corporation implemented Iridium, a satellite-based wireless personal communications satellite system (PCSS) •
Honeycomb
the pattern that fits the cellular concept
•
defined by its physical size; its physical size varies depending on user density and calling patterns
Cell
•
the smallest cells used most often in highdensity areas such as found in large cities and inside buildings; exhibit milder propagation impairments such as reflections and signal delays
Microcells
these is used in well-shielded areas or areas with high levels of interference
Picocells
•
normally used in center-excited cells (center of Omnidirectional antennas the cell) •
are used in edge- and corner- excited cells (three of the cell’s six vertices) •
Sectored directional antennas
the process in which the same set of Frequency reuse frequencies (channels) can be allocated to more than one cell, provided the cells are separated by sufficient distance •
a geographic cellular radio containing three groups of cells •
coverage area
Clusters
•
when the area of a cell, or independent component coverage area of a cellular system is further divided, thus creating more cell areas; to increase the channel capacity and improve the availability and reliability of a cellular telephone network
Cell splitting
•
the point when a cell reaches maximum capacity occurs when the number of subscribers wishing to place a call at any given time equals the number of channels in the cell
Maximum traffic load
•
decreasing co-channel interference while increasing capacity by using directional antennas
Sectoring
placing two receive antennas; improves reception by effectively providing a larger target for
Space diversity
•
60
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
signals radiated from mobile units •
divides a group of channels into smaller groupings or segments of mutuality exclusive frequencies; cell sites, which are within the reuse distance, are assigned their own segment of the channel group; a means of avoiding co-channel interference, lowers the capacity of a cell by enabling reuse inside the reuse distance
Segmentation
•
means of avoiding full-cell splitting where the entire area would otherwise need to be segmented into smaller cells
Dualization
•
the locations of these radio-frequency transceivers; serves as central control for all users within that cell
Base stations
•
when mobile unit moves possibly from one company’s service area into another company’s service area
Roaming
•
the transfer of a mobile unit from one base station’s control to another base station’s control
Handoff (handover)
•
a connection that is momentarily broken during the cell-to-cell transfer
Hard handoff
a flawless handoff; no perceivable interruption of service and normally takes approximately 200 ms which is imperceptible to voice telephone users although the delay may be disruptive when transmitting data
Soft handoff
•
a protocol aligns with a subprotocol of the SS7 IS-41 protocol stack that facilitates communications among databases and other network entities; allow mobile units to roam and to perform handoffs of calls already in progress when a mobile unit moves from one cellular system into another without subscriber intervention •
•
the process where a mobile unit notifies a serving MTSO of its presence and location through a base station controller
Autonomous registration
operates under the direction o switching center (MTSO); manage each of the radio channels at each site, supervises calls, turns the radio transmitter and receiver on and off, injects data onto the control and voice channels and performs diagnostic tests • second part of the base station controllers
Cell-site controller
•
61
Base (BTS)
transceiver
station
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
•
also a part of the base station subsystem; used with cellular telephone system voice channels can be either narrowband FM for analog system
Radio transceivers
•
generally used to connect switching centers to cell sites and to the public telephone network
Four-wire leased lines
•
governs the way telephone calls are established and is disconnected
Communications protocol
•
the actual voice channel where mobile users communicate directly with other mobile and wireline subscribers through a base station
User channel
is used for transferring control and diagnostic information between mobile users and a cellular telephone switch through a base station
Control channel
•
CHAPTER 20 Cellular Telephone Systems a standard cellular telephone service (CTS) initially placed into operation on October 13, 1983; the idea was to eliminate the possibility of a monopoly and provide the advantages that generally accompany a competitive environment
Advanced Mobile Telephone System (AMPS)
a transmission mode transmit in both directions
Duplexing
•
•
that
simultaneously
•
a 34-bit binary code comprised of a three-digit area code, a three-0digit prefix (exchange number), and a four-digit subscriber (extension) number
Mobile identification number (MIN)
•
a 32-bit binary code permanently assigned to each mobile unit
Electronic (ESN)
•
indicates whether the terminal has access to all 832 AMPS channel ; specifies the maximum radiated power for the unit
Four-bit station (SCM)
a 15-bit binary code issued by the FCC to an operating company when it issues it a license to provide AMPS cellular service to an area
System identifier (SID)
•
•
combination of cellular telephone networks and 62
Personal
serial
number
class
mark
Communications
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
the Intelligent Network which is the entity of the SS7 interoffice protocol that distinguishes the physical components of the switching network
System (PCS)
•
a database that stores information about the user, including home subscription information and what supplementary services the user is subscribed to
Home location register (HLR)
•
a database that stores information about subscribers in a particular MTSO serving area
Visitor location register (VTR)
a database that stores information pertaining to the identification and type of equipment that exist in the mobile unit
Equipment registry (EIR)
•
identification
allows all calls to pass through the network to Available mode the subscriber except for a minimal number of telephone numbers that can be blocked •
•
the PCS equivalent to caller ID; the name of the calling party appears on the mobile unit’s display, which allows PCS users to screen calls
Screen mode
•
all calls except those specified by the subscriber are automatically forwarded to a forwarding destination without ringing the subscriber’s handset
Private mode
•
no calls are allowed to pass through to the subscriber
Unavailable mode
•
was originally intended to provide a short-term solution to the traffic congestion problem in the AMPS system
Narrowband AMPS (N-AMPS)
•
used by mobile units to request access to the cellular telephone system; a unidirectional channel specified for transmissions from mobile-to-base units only
RACH
•
used to transmit information from base stations to specific mobile stations;
SPACH
•
channels used to carry generic, system-related information; a unidirectional base station-to-mobile unit transmission shared by all mobile units
BCCH
an access method used with standard analog AMPS
FDMA
•
•
was first used by the military to ensure reliable 63
Frequency-hopping
spread
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
antijam and to secure communications in a battlefield environment; the fundamental concept is to break a message into fixed-size blocks of data with each block transmitted in sequence except on a different carrier frequency
spectrum
•
a high-bit rate pseudorandom code is added to a low-bit rate information signal to generate a highbit-rate pseudorandom signal closely resembling noise that contains both the original data signal and the pseudorandom code
Direct-sequence spectrum
a second-generation cellular telephone system initially developed to solve the fragmentation problems inherent in first-generation cellular telephone system
Global System for Mobile Communications (GSM)
•
•
basic parameters of GSM
•
• • •
• •
•
GMSK modulation (Gaussian MSK) 50 MHz bandwidth FDMA/TDMA accessing eight 25-kHz channels w/in each 200-kHz traffic channel 200 kHz traffic channel 992 full-duplex channels supplementary integrated services digital network (ISDN) services
•
a satellite-based wireless personal communications network designed to permit a wide range of mobile telephone services, including voice, data, networking, facsimile and paging • uses 66 satellites
Iridium
•
the unique key to the Iridium system and the primary differentiation between Iridium
Satellite cross-links
relay information to the terrestrial gateways and the system control segment located at the earth stations
Feeder links
•
spread
CHAPTER 21: Introduction to Data Communications and Networking •
Data are systems of interrelated computers and computer equipment and can be as simple as a network personal computer connected to a printer or two personal computers connected together through
64
communications
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
the public telephone network •
one of the earliest means of communicating electrically coded information when a proposal submitted to a Scottish magazine suggested running a communications line between villages comprised of 26 parallel wires
1753
•
Carl Friedrich gauss developed an unusual system based on a five by five matrix representing 25 letters
1833
•
the first successful data communications system was invented. the first practical data communications code.
1832
Morse secured an American patent for the telegraph. the first telegraph line was established between Baltimore and Washington dc with the first message conveyed over this system.
1840
•
•
•
•
Morse code
1844
1860
high speed printers were available
•
Emile Baudot invented a telegraph multiplexer which allowed signals from up to six different telegraph machines to be transmitted simultaneously over a single wire.
1874
•
the telephone graham bell
Alexander
1875
•
Guglielmo Marconi succeeded in sending radio telegraph messages
1899
•
the first commercial radio stations carrying voice information were installed
1920
•
he demonstrated a sometime in the late 1930s
Konrad Zuis
•
the first special purpose computer using electromechanical relays for performing logical operations batch processing systems were replaced by online processing systems with terminals connected directly to the computer through serial or parallel communications lines.
1940
the year introduced microprocessor controlled microcomputers.
1970s
•
•
was
invented
by
computing
machine
65
1960s
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
•
personal computers became an essential item in the home and workplace.
ATM components
•
1980s
•
•
•
•
1.4 Gbps
ATM speeds
•
a digital telecommunications technology that can simultaneously transmit voice and data over the same pair of telephone wires ISDN channels:
•
routers and switches to connect carrier on global basis backbone devices to connect all the lans within a large organization switches and adapters which link desktop computers to high speed atm connection for running multimedia applications
ISDN
• • •
B-channel (Bearer channel) D channel H channel
•
used to carry the digital information; build block of the ISDN; 64 kbps
B-channel
•
used to carry signaling and supervisory information to the network; kpbs (bri) or 64 kbps (pri)
D channel
•
provide for user information at higher bit rates; combination of several b channels
H channel
•
for business with larger data needs; American 23b + d(t1 = 1.544mbps); European 30b + d (e1= 2.048 mbps)
PRI
•
150 mbps; for future HDTV projects; h channels
Broadband ISDN
CHAPTER 22: Fundamental Concepts of Data Communications the first fixed-length character code developed for machines rather than for people; named after Emile Baudot, an early pioneer in telegraph printing; a fixed-length source code; all characters are represented in binary and have the same number of symbols (bits) •
66
Baudot Code
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA •
the standard character set for source coding the alphanumeric character set that humans understand but computers do not; a seven-bit fixed length character set
United States of America Standard Code for Information Exchange (ASCII)
•
an eight-bit fixed-length character developed in 1962 by the International Business Machines Corporation (IBM); used almost exclusively with IBM mainframe computers and peripheral equipment
Extended Binary-Coded Decimal Interchange Code (EBCDIC)
are those omnipresent black-and-white striped stickers that seem to appear on virtually every consumer item in the United States and most of the rest of the world; a series of vertical black bars separated by vertical white bars
Bar codes
•
has spaces or gaps between characters; each Discrete code character within the bar code is independent of every other character •
•
does not include spaces between characters
Continuous code
•
stores data in two dimensions in contrast with a conventional linear bar code
2D code
•
uses an alphanumeric code similar to the ASCII code; consists of 36 unique codes representing the 10 digits and 26 uppercase letters
Code 39 (Code 3 of 9, 3 of 9 Code)
•
developed sometime in the early 1970s to identify the products of the grocery industry; found on virtually every grocery item from a candy bar to a can of beans
Universal Product Code (UPC)
•
only one bit within a given data string is in error; affects only one character within a message
Single bit error
when two or more non-consecutive bits within a given data string are in error; can affect one or more characters within a message
Multiple bit error
•
•
the first fixed length character code developed for machines rather than people
Baudot code
a French postal engineer who developed the Baudot code
Thomas Murray
•
•
RTTY is the acronym for _____
Radio teletype
•
a fixed length source code
Baudot code
67
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA •
the standard character set for source coding the alphanumeric character set that humans understand
ASCII
an eight bit fixed length character set developed in 1962 by IBM
EBCDIC
•
•
Extended binary coded decimal interchange code
EBCDIC is the acronym for ___
•
when two or more consecutive bits within a given data string re in error; can affect one or more characters within a message
Burst error
the process of monitoring data transmission and determining when errors have occurred; not to prevent errors from occurring but to prevent undetected errors from occurring
Error detection
•
duplicating each data unit for the purpose of Redundancy detecting errors; an effective but rather costly means of detecting errors, especially with long messages •
adding bits for the sole purpose of detecting errors •
•
probably the simplest error-detection scheme
•
own error-detection bit
Redundancy checking
Vertical redundancy checking (VRC) (character parity, parity) Parity bit
•
the parity bit is always a 1; useful only when errors occur in a large number of bits
Marking parity
•
another relatively simple form of redundancy error checking where each character has a numerical value assigned to it; appended to the end of the message
Checksum
•
Longitudinal Checking (LRC)
a redundancy error detection scheme that use parity to determine if a transmission error has occurred with a message and is therefore sometimes called message parity •
Redundancy
Block check sequence (BCS) or Frame check sequence (FCS)
the bit sequence for the LRC
probably the most reliable redundancy checking technique for error detection; a convolutional scheme; approximately 99.999% of all transmission errors are detected •
68
Cyclic (CRC)
redundancy
checking
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
•
include enough redundant information with each transmitted message to enable the receiver to determine when an error has occurred
Error-detecting codes
include sufficient extraneous information along with each message to enable the receiver to determine when an error has occurred and which bit is in error
Error-correcting codes
•
•
two primary methods used for error-correction:
• •
retransmission forward error correction
CHAPTER 23: Data-Link Protocols and Data Communications Networks the primary goal is to give users of a network the tools necessary for setting up the network and performing data flow control •
•
arrangements between people or processes
Network architecture
Protocols
•
a set of rules implementing and governing an orderly exchange of data between layer two devices such as line control units and front-end processors
Data-link protocol
•
all stations have equal access to the network, but when they have a message to transmit, they must contend with the other stations on the network for access to the transmission medium
Peer-to-peer network
•
determines which device is transmitting and which is receiving at any point in time
Line discipline
•
coordinates the rate at which data are transported over a link and generally provides an acknowledgement mechanism that ensures that data are received at the destination
Flow control
•
a solicitation sent from the primary to a secondary to determine if the secondary has data to transmit
Poll
•
how the primary designates a secondary as a destination or recipient of data
Selection
the transmitting station sends one message frame and then waits for an acknowledgement
Stop-and-wait flow control
•
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Engr. Jaime P.
Licuanan, CCNA
before sending the next message frame •
a source station can transmit several frames in succession before receiving an acknowledgement
Sliding window flow control
refers to imaginary receptacles at the source and destination stations with the capacity of holding several frames of data
Sliding window
•
interpret a frame of data as a group of Character-oriented protocols successive bits combined into predefined patterns of fixed length usually eight bits •
•
a discipline for serial-by-bit information transfer over a data communications channel
Bit-oriented protocol
•
are relatively simple, character-oriented generally used on two-point networks using asynchronous data and asynchronous modems
Asynchronous protocols
data-link
•
remote stations can have more than one PC or printer
Synchronous protocols
data-link
group of computers, printers, and other digital devices • a synchronous character-oriented data-link protocol developed by IBM; sometimes called bisync or bisynchronous communications
Cluster
•
a synchronous bit-oriented protocol developed in the 1970s by the IBM for use in system network architecture environment
Synchronous data-link control (SLDC)
•
an information field is not allowed; cannot be used to transfer numbered information
Supervisory frame
causes all previously set functions to be cleared by the secondary
Clear
•
•
•
Binary synchronous communications (BSC)
Beacon test
causes the secondary to turn on or turn off
causes the addressed secondary station to place itself into the monitor mode
Monitor mode
causes a secondary station to transmission directly to its receiver input
Wrap
•
•
•
loop
its
make a receiver transparent to all data located
a switched data communications network similar to the public telephone network except it is designed for transferring data only •
•
involves dividing data messages into small
70
Transparency Public switched data network (PDN or PSDN)
Packet switching
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
bundles of information and transmitting them through communications networks to their intended destinations using computer-controlled switches logically equivalent to a two-point dedicated private-line circuit except slower •
Permanent (PVC)
virtual
users send small packets of data into the Datagram (DG) network service • the integrating of a wide range of services into a Integrated (ISDN) network single multipurpose network; a network that proposes to interconnect an unlimited number of independent users through a common communication network
circuit
•
digital
•
provides the most economical and effective means of handling local data communication needs
Local area network (LAN)
the time it takes a signal to travel from a source to a destination
Propagation delay
•
CHAPTER 24: Microwave Radio Communications and System Gain •
described as electromagnetic waves with frequencies that range from approximately 500 MHz to 300 GHz or more
Microwave
•
systems are those used to carry information for relatively long distances
Long-haul microwave systems
•
propagate signals through Earth’s atmosphere between transmitters and receivers often located on top of towers spaced about 15 miles to 30 miles apart
Microwave radios
•
the composite signal that modulates the FM carrier
Baseband
•
a preemphasis network precedes the FM deviator; provides an artificial boost in amplitude to the higher baseband frequencies
Microwave transmitter
•
a receiver and a transmitter placed back to back or in tandem with the system
Microwave repeaters
another name for local oscillator and is considerably lower in frequency than either the received or the transmitted radio frequencies
Shift oscillator
•
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Electronics Systems and Technologies
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Licuanan, CCNA •
Radio fade
the reduction in signal strength
•
it suggests that there is more than one transmission path or method of transmission available between a transmitter and a receiver; used to increase the reliability of the system by increasing its availability
Diversity
•
simply modulating two different RF carrier frequencies with the same IF intelligence, then transmitting both RF signals to a given destination
Frequency diversity
•
the output of a transmitter is fed to two or more antennas that are physically separated by an appreciable number of wavelengths
Space diversity
•
a single RF carrier is propagated with two different electromagnetic polarizations
Polarization diversity
•
using more than one receiver for a single radiofrequency channel
Receiver diversity
•
it combines frequency, space, polarization and receiver diversity into one system
Quad diversity
somewhat specialized form of diversity that consists of a standard frequency-diversity path where the two transmitter/receiver pairs at one end of the path are separated from each other and connected to different antennas that are vertically separated as in space diversity
Hybrid diversity
•
provide protection for a much larger section of Protection the communications system that generally includes arrangement several repeaters spanning a distance of 100 miles or more •
•
two types of protection switching arrangement:
• •
switching
hot standby diversity
•
each working radio channel has a dedicated backup or spare channel
Hot standby protection
•
a single backup channel is made available to as many as 11 working channels
Diversity protection
•
points in the system where baseband signals either originate or terminate
Terminals
points in a system where baseband signals may be reconfigured or where RF carriers are simply repeated or amplified
Repeater stations
•
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a balanced modulator that when used in conjunction with a microwave generator, power amplifier, and bandpass filter, up-converts the IF carrier to an RF carrier and amplifies the RF to the desired output power •
Transmit (transmod)
modulator
a unidirectional device often made from a Isolator ferrite material; used in conjunction with a channelcombining network to prevent the output of one transmitter from interfering with the output of another transmitter •
•
this occurs when three stations are placed in a geographical straight line in the system
Multihop interference
•
preventing the power that leaks out the back and sides of a transmit antenna from interfering with the signal entering the input of a nearby receive antenna
Ring around
•
the line-of-sight path directly between the transmit and receive antennas
Free-space path
•
the portion of the transmit signal that is reflected off Earth’s surface and captured by the receive antenna
Ground-reflected wave
•
consists of the electric and magnetic fields associated with the currents induced in Earth’s surface
Surface wave
•
the portion of the transmit signal that is returned back to Earth’s surface by the ionized layers of Earth’s atmosphere
Sky wave
•
often defined as the loss incurred by an electromagnetic wave as it propagates in a straight line through a vacuum with no absorption or reflection of energy from a nearby objects
Free-space path loss
•
a phenomena where in no electromagnetic is actually lost or dissipated – it merely spreads out as it propagates away from the source resulting in lower relative power densities
Spreading loss
•
the reduction in receive signal level; reduction in signal strength at the input to a receiver; it applies to propagation variables in the physical radio path that affect changes in the path loss between transmit and receive antennas
Fading
the difference between the nominal output power of a transmitter and the minimum input
System gain
•
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power to a receiver necessary to achieve satisfactory performance; must be greater than or equal to the sum of all gains and losses incurred by a signal as it propagates from a transmitter to a receiver essentially a fudge factor included in system gain equations that considers the nonideal and less predictable characteristics of radiowave propagation, such as multipath propagation and terrain sensitivity; these characteristics cause temporary, abnormal atmospheric conditions the minimum wideband carrier power at the • input to a receiver that will provide a usable baseband output
Fade margin (link margin)
•
simply a ratio of input signal-to-noise ratio to output signal-to-noise ratio
Noise factor
indicates how much the signal-to-noise ratio deteriorates as a waveform propagates from the input of a circuit
Noise figure
•
•
Receiver threshold sensitivity)
(receiver
CHAPTER 25 : Satellite Communications in astronomical terms, a celestial body that orbits around a planet; in aerospace terms, a space vehicle launched by humans and orbits Earth or another celestial body •
Satellites
a microwave repeater in the sky that consists of Communications satellite a diverse combination of one or more of the following: receiver, transmitter, amplifier, regenerator, filter, onboard computer, multiplexer, demultiplexer, antenna, waveguide and about nay other electronic communications circuit ever developed •
•
Satellite radio repeater
called a transponder
consists of one or more satellite space vehicles, Satellite system a ground-based station to control the operation of the system and a user network of earth stations that provides the interface facilities for the transmission and reception of terrestrial communications traffic •
•
includes control mechanisms that support the payload operation
Bus
the actual user information conveyed through the system
Payload
•
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Electronics Systems and Technologies
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a continuously transmitted unmodulated carrier that an earth station can lock on to and use to determine the exact location of a satellite so the earth station can align its antennas
Beacon
accomplished transmission
Echo
•
the
•
first
transatlantic
•
meaning lightning
Molniya
•
Kepler’s laws:
•
•
•
the planets move in ellipses with the sun at one focus the line joinining the sun and a planet sweeps out equal areas in equal intervals of time (laws of areas) the square of the time of revolution of a planet divided by the cube of its mean distance from the sun gives a number that is the same for all planets (harmonic law)
•
closest approach to the earth
Perigee
•
farthest point from earth
Apogee
•
rotate around the Earth in an elliptical or circular pattern
Orbital (nonsynchronous)
the orbit if the satellite is orbiting in the same direction as Earth’s rotation (counterclockwise) and at an angular greater than that of earth
Prograde or posigrade orbit
•
satellites
the orbit if the satellite is orbiting in the Retrograde orbit opposite direction of Earth’s rotation or in the same direction with an angular velocity less than that of Earth •
•
a system utilizing a 66-satellite constellation orbiting approximately 480 miles above Earth’s surface; the main advantage is that the path loss between earth stations and space vehicles is much lower than for satellites revolving in medium- or high-altitude orbits
Low Earth Orbit
operate in the 1.2 GHz to 1.66 GHz frequency band and orbit between 6000 miles and 12000 miles above the Earth
Medium Earth Orbit
•
•
high-altitude
earth-orbit
satellites
operating 75
Geosynchronous satellites
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
primarily in the 2 GHz to 18 GHz frequency spectrum with orbits 22 300 miles above the Earth’s surface •
the line joining the perigee and apogee the center of Earth
Major Axis (line of apsides)
the line perpendicular to the major axis and halfway between the perigee and apogee
Minor axis
•
•
Semiminor axis
half the distance of the minor axis
all satellites rotate around Earth in an orbit that Geocenter forms a plane that passes through the center of gravity of Earth •
•
are virtually all orbits except those that travel directly above the equator or directly over the North and South Poles
Inclined Orbits
the angle between the Earth’s equatorial plane and the orbital plane of a satellite measured counterclockwise at the point in the orbit where it crosses the equatorial plane traveling from south to north
Angle of inclination
•
•
Ascending node
traveling from south to north
•
the point where a polar or inclined orbit crosses the equatorial plane traveling from north to south
Descending node
•
the line joining the ascending an descending nodes through the center of Earth
Line of nodes
•
when the satellite rotates in an orbit directly above the equator, usually in a circular path
Equatorial orbit
•
when the satellite rotates in a path that takes it over the North and South poles in an orbit perpendicular to the equatorial plane
Polar orbit
•
causing elliptical orbits to rotate in a manner that causes the apogee and perigee to move around the Earth
Rotation of the line of apsides
•
satellites appear to remain in a fixed location above one spot on earth’s surface
Geosynchronous geostationary)
the process of maneuvering a satellite within a preassigned window
Station keeping
•
•
the circumference of a geosynchronous orbit
264 790 km
•
the velocity of a geosynchronous satellite
6840 mph
76
(stationary
or
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
•
sometimes referred to geosynchronous earth orbit
Clarke orbit or Clarke belt
•
direction of maximum gain of an earth station antenna
Boresight
azimuth and elevation angle are jointly referred to __________
Look angles
•
•
Subsatellite point (SSP)
a point on the surface below the satellite
•
the vertical angle formed between the direction of travel of an electromagnetic wave radiated from an earth station antenna pointing directly toward a satellite and the horizontal plane
Angle of elevation
•
the horizontal angular distance from a reference direction either the southern or northern most point of the horizon
Azimuth
•
defined as the horizontal pointing angle of an earth station antenna
Azimuth angle
•
determine the farthest satellite away that can be seen looking east or west of the earth station’s longitude
Line-of-sight limits
•
uses the angular momentum of its spinning body to provide roll and yaw stabilization
Spinner satellite
•
the body remains fixed relative to Earth’s surface, while an internal subsystem provides roll and yaw stabilization
Three-axis stabilizer satellites
the geographical representation of a satellite antenna’s radiation pattern; the area on Earth’s surface that the satellite can receive from or transmit to • the smallest beams; concentrate their power to very small geographical areas and, therefore, typically have proportionately higher EIRPs than those targeting much larger areas because a given output power can be more concentrated
Footprint (footprint map)
typically target up to 20% of the Earth’s surface and, therefore, have EIRPs that are 3 dB or 50% lower than those transmitted by spot beams that typically cover only 10% of the Earth’s surface
Hemispherical antennas
•
•
Spot beams
have a beamwidth of approximately 42% of Earth coverage Earth’s surface which is the maximum view of any one geosynchronous satellite •
77
downlink
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA •
increasing the size of an antenna, the beamwidth of the antenna is also reduced thus, different beams of the same frequency can be directed to different geographical areas of Earth
Frequency reuse
•
consists of an input bandlimiting device (BPF), an input low-noise amplifier (LNA), a frequency translator, a low-level power amplifier, and an output bandpass filter
Satellite transponder
•
used when it is necessary to communicate between satellites
Cross-links or intersatellite links (ISLs)
•
high power amplifiers used in earth station transmitters and the traveling-wave tubes typically used in a satellite transponders
Nonlinear devices
the amount the output level is backed off from rated levels equivalent to a loss
Back-off loss
•
•
Effective isotropic power (EIRP)
defined as an equivalent transmit power
radiated
a hypothetical value that can be calculated but Equivalent noise temperature cannot be measured; often used rather than noise figure because it is more accurate method of expressing the noise contributed by a device or a receiver when evaluating its performance •
•
the noise power normalized to a 1-Hz band width, or the noise power present in a 1-Hz bandwidth
Noise density
•
the average wideband carrier power-to-noise density ratio
Carrier-to-noise density ratio
•
the combines power of the carrier and its associated sidebands
Wideband carrier power
the thermal noise present in a normalized 1-Hz bandwidth
Noise density
•
CHAPTER 26: Satellite Multiple Accessing Arrangements
•
sometimes
called
multiple
destination
78
Multiple accessing
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
because the transmission from each earth station are received by all the other earth stations in the system method of assigning adjacent channels different electromagnetic polarization •
•
Frequency reuse
Anik
an Eskimo word meaning “little brother”
•
a method required when three or more earth stations wish to communicate with each other
Multiple accessing
•
sometimes called to multiple accessing because the transmissions from each earth station are received by all the other earth stations in the system
Multiple destination
•
when it is used, a given number of the available voice-band channels from each other station are assigned a dedicated station
Preassignment
•
voice-channels are assigned on an as-needed basis; provides more versatility and more efficient use of the available frequency spectrum
Demand assignment
each earth station’s transmissions are assigned specific uplink and downlink frequency bands within an allotted satellite; transmissions are separated in the frequency domain
FDMA
•
each earth station transmits a short burst of TDMA information during a specific time slot (epoch); transmissions are separated in the time domain; the entire transponder bandwidth and power are used for each transmission but for only a prescribed interval of time •
the entire satellite transponder bandwidth is used by all stations on a continuous basis; signal separation is accomplished with envelope encryption/decryption techniques •
•
CDMA
Demand-assignment, access (DAMA)
an alternate channel allocation scheme
multiple
•
an acronym for single-channel-per-carrier PCM multiple-access d emand-assignment equipment
SPADE
•
Common signaling channel (CSC)
a time-division-multiplexed transmission that is frequency-division multiplexed into the spectrum below the QPSK-encoded voice-band channels with a 160 KHz bandwidth •
called when each stations can transmit only 79
Store-and-forward system
Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
during their specified time slot although the incoming voice-band signals are continuous
•
Chip code
a unique binary word
•
produced when a bipolar data-modulated signal is linearly multiplied by the spreading signal in a special balanced modulator
Direct-sequence spectrum (DS-SS)
•
a form of CDMA where a digital code is used to continually change the frequency of the carrier
Frequency hopping
•
there can be more TCs assigned than there are SCs
Channel compression
•
a phenomenon when speech energy is detected on a TC and there is no SC to assign it to
Competitive clipping
•
a form of analog channel compression that has been used for suboceanic cables for many years
Time-assignment interpolation (TASI)
can be defined as the art or science of plotting, ascertaining, or directing the course of movements; knowing where you are and being able to find your way around
Navigation
•
spread
speech
the most ancient and rudimentary method of Wandering navigation; is simply continuing to travel about until you reach your destination •
•
direction and distance are determined from precisely timed sightings of celestial bodies including the stars and moon; a primitive technique that dates back thousand of years
Celestial navigation
•
another rudimentary method of navigation; fixing a position and direction with respect to familiar, significant landmarks, such as railroad tracks, water towers, barns, mountain peaks and bodies of water
Piloting
•
a navigation technique that determines position by extrapolating a series of measured velocity increments used quite successfully by Charles Lindbergh in 1927 during his historic 33 hour transatlantic journey and quite unsuccessfully by Amelia Earhart in 1937 during her attempt to make first around-the-world flight
Dead reckoning
the most accurate navigation technique; position is determined by measuring the travel time of an electromagnetic wave as it moves from a transmitter to a receiver
Radio or electronic navigation
•
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Electronics Systems and Technologies
Engr. Jaime P.
Licuanan, CCNA
•
consist of 24 operational satellites revolving around Earth in six orbital planes approximately 60° apart with four satellites in each plane; there are 21 working satellites and three satellites reserved as spaces
Space segment
•
this unique number is used to encrypt the signal from that satellite
Pseudorandom noise (PRN) code
•
a term generally associated with a table showing the position of a heavenly body on a number of dates in a regular sequence, in essence, an astronomical almanac
Ephemeris
•
the Navstar control segment which includes all the fixed-location ground-based monitor stations located throughout the world a master control station (MCS), and uplink transmitters
Operational (OCS)
makes GPS even more accurate; works by canceling out most of the natural and man-made errors that creep into normal GPS measurements
Differential GPS
•
-end-
81
control
system
