AFG3000 The Next Generation o Signal Generation Glossary
Signal Sources or Design Veri cation Introduction
Applications
Signal sources are used to generate wave orms as a stimulus or electronic measurements. Most circuits require some type o Signal sources have hundreds o di erent applications but in the electronic measurement context they all into three basic input signal whose amplitude varies over time. The signal may be a sine wave or other analog unction, a digital pulse, a binary categories: veri cation, characterization, and stress/margin testing. Representative applications include: pattern, or a purely arbitrary wave shape. The signal source can provide “ideal” wave orms or it may add known, repeatable Verifcation - Analyzing Digital Modulation: Wireless equipment designers developing new transmitter and receiver hardware amounts and types o distortion (or errors) to the signal it delivers. This characteristic is one o the signal source’s greatest must simulate baseband I&Q signals – with and without impairments – to veri y con ormance with wireless standards. A dual virtues, since it is o ten impossible to create predictable distortion exactly when and where it is needed using only the circuit channel Arbitrary Function Generator can generate modulation signals with ne phase resolution between I and Q which is used itsel . The response o the DUT (Device Under Test) in the presence o these distorted signals reveals its ability to handle to modulate a traditional RF signal source. DUT response is measured using a spectrum analyzer. stresses that all outside the normal per ormance envelope. Characterization - Testing D/A and A/D Converters: Newly-developed digital-to-analog converters (DAC) and analog-to-digital Most signal sources today are based on digital technology. Many can ul ll both analog and digital requirements, although the converters (ADC) must be exhaustively tested to determine their limits o linearity, monotonicity, and distortion. A state-o -the-art most e cient solution is usually a source whose eatures are optimized or the application at hand – either analog or digital. AWG can generate simultaneous, in-phase analog and digital signals to drive such devices at speeds up to 1 Gbps. Signal Source Classifcation
Stress/Margin Testing - Stressing Communication Receivers: Engineers working with serial data stream architectures (commonly used in digital communications buses and disk drive ampli ers) need to stress their devices with impairments, particularly jitter and timing violations. Advanced signal sources save the engineer untold hours o calculation by providing e cient built-in jitter editing and generation tools.
Mixed Signal Sources: Type o signal source that outputs analog wave orms and digital patterns. Function Generator: Outputs standard wave orms, such as a sine wave or a rectangle wave. Arbitrary Wave orm Generator: Generates wave orms de ned by individual user pre erence.
S a m p l ol ck Pulse Generator: Drives stream o square waves or pulses rom small number o outputs ( ri le ar te) Pattern Generator (or Data Generator): Generates digital pattern o many channels
C o u n
t r
e
m DUT r
W a v e fo M e m o
Two undamentally di erent concepts exist to generate arbitrary wave orms: True Arbitrary Wave orm Generator (True Arb) C o f l ck ( i Direct Digital Synthesis (DDS) True Arbitrary Wave orm Generator (True Arb) The synthesizer generates the signal by recalling wave orm points rom memory. y Fre enc With each clock cycle, the next point in memory is recalled. Frequency tuning is achieved by varying the clock rate. C o n o tr l
Counter
Test Point
g
s
a
u
u
a
W a v
o
cc m l t r
ull circle. The output
Output
A phase accumulator determines the next point to be recalled by incrementing the phase by a xed angle with each clock cycle. The clock rate is constant.
k i Frequency tuning is lachieved by varying the phase increment . Large increments lead to high- requencies, as the phase accumulator completes the circle aster. At high rates, wave orm points are skipped. At low rates, identical points are output several times. C
F re q u e n c y C o n tro
(f x e d
l
i
re g s te r
Frequency Control
Phase register
l
Standard of reference waveform Add Impairments
Phase accumulator
Signal Shi t Keying Amplitude Shi t Keying (ASK)
M e m o r y
A type o digital modulation in which the digital modulating signal causes the output requency to switch between two amplitudes.
DAC
Waveform Memory
Frequency Shi t Keying (FSK)
Basic Wave orms
Pulse Characteristics
Sine Wave
Rise Time
A curved wave shape de ned by the mathematical sine unction.
A wave shape consisting o repeating square pulses.
Amount o time required or a pulse edge to transition rom low to high level. Fall Time Phase Shi t Keying (PSK) Amount o time required or a pulse edge to transition rom A type o digital modulation in which the carrier switches between two phase settings. high to low level. Pulse Width
Sawtooth Wave
Amount o time the pulse takes to go rom low to high and back to low again, measured at 50% o ull voltage.
Square Wave
A wave orm that ramps up slowly, W a v e fo m p o n s n m e m o y then alls o r quickly. i t i r v f rm e
o
s
e
A type o digital modulation in which the carrier switches between two requencies.
Wave orm Modulation
Amplitude Modulation (AM) A type o analog modulation in which amplitude variations embed lower- requency in ormation into a carrier signal o higher requency: most commonly used in broadcast communications.
Period
int in m m ry
Triangle Waves
o
Pulse Width
A wave orm with symmetrical rise and all times. Pulse Wave
Wave orm Characteristics Amplitude
A measure o the voltage ‘‘strength’’ o a wave orm. Amplitude is constantly changing in an AC signal. Frequency
90%
10%
Fall Time
Swept Wave orms
Amplitude Sweep
Phase
A wave orm that increases in time.
Pulse – A common wave orm shape that has a ast rising edge, a width, and a ast alling edge. Pulse Pattern Generator – A type o logic signal source that can drive a stream o square waves or pulses rom a small number o outputs, usually at very high- requencies. Also known as a pulse generator.
Pulse Width – The amount o time the pulse takes to go rom low to high and back to low again, conventionally measured at50% o ull voltage. Pulse Width Modulation (PWM) – A type o digital modulation in which the modulating signal causes the active pulse width o the pulse to vary, applicable to pulse wave orms only; commonly used in digital audio systems. Quadrature (IQ) Modulation Technology – A type o modulation in which two carriers, an in-phase (I) wave orm and a quadrature-phase (Q) wave orm, are combined and transmitted over one channel, then separated and demodulated at the receiving end; commonly ound in today’s wireless communications networks. Ramps – Transitions between voltage levels o sine waves that change at a constant rate. Record Length – The number o wave orm points used to create a record o a signal, re erred to as memory depth in analog/mixed-signal generators and pattern depth in logic signal generators. Rectangular Wave – A wave in which the switching characteristics are similar to those o a square wave, except that the high and low time intervals are not o equal length.
Sampling – The process used to dene a signal using samples, or data points, that represent a series o voltage measurements along the slope o a wave orm.
Direct Digital Synthesizer (DDS) Technology – Technology that synthesizes wave orms by using a single Sample Point – Data points that represent a series o voltage measurements along the slope o a clock requency to spawn any requency within the instrument’s range; determines the rate at which sampleswave orm; the raw data rom an ADC used to calculate wave orm points. are clocked out o a signal generator’s memory. Sample Rate – The rate at which an analog/mixed-signal generator can output ull wave orm cycles, Distortion – A by-product o circuit realities, like distributed capacitance, crosstalk, and more. usually speci ed in terms o megasamples or gigasamples per second; also known as clock rate or sampling requency. Duty Cycle – The variation o a wave or pulse in which the high and low time intervals are not o equal Sawtooth Wave – A wave in which the voltage ramps up slowly and evenly to a peak in each cycle, length; the ratio o the positive duration o a pulse to its negative or zero duration. then alls o quickly. Fall Time – Amount o time required or a pulse edge to make a transition to a state opposite its current level; Signal Fidelity – The accurate reconstruction o a signal, determined by the systems and per ormance in the case o rise time, rom low level to high level and, in the case o all time, rom high level to low level. considerations o the stimulus or acquisition instrument. Filtering – The process by which a signal generator removes selected bands o requency rom a signal; can Signal Modulation – A process in which signal amplitude, phase and/or requency variations embed be used to prevent unwanted aliasing distortion in the DUT output. lower- requency in ormation into a carrier signal o higher- requency. Flatness – The degree which changes level with output requency when outputting a sine wave. Signal Source or Signal Generator – A test device used to inject a signal into a circuit input; the circuit’s Frequency – The number o times a signal repeats in one second, measured in Hertz (cycles per second). output is then read by an oscilloscope or logic analyzer; also known as a signal generator. Frequency equals 1/period. Simulation – A technique used by a signal generator to output a wave orm that mimics the output o a Frequency Modulation (FM) – A type o analog modulation in which requency variations embed lowerdevice or use in testing another device. requency in ormation into a carrier signal o higher- requency; most commonly used in broadcast Sine Wave – A common curved wave shape that is mathematically dened. communications. Frequency Shi t Keying (FSK) – A type o digital modulation in which the carrier switches between two
requencies, its center requency and an o
set requency.
Slope – On a graph or an instrument’s screen, the ratio o a vertical distance to a horizontal distance. A positive slope increases rom le t to right, while a negative slope decreases rom le t to right.
Function Generator (FG) – A type o signal generator that outputs undamental waves, such as a sine wave
Square Wave – A common wave shape consisting o repeating square pulses; a voltage that switches
Gigahertz (GHz) – 1,000,000,000 Hertz; a unit o
Step – A wave orm that shows a sudden change in voltage.
or a rectangle wave.
requency.
Graphic Editor – An integrated tool within a signal generator that allows you to construct and view a literal
representation o the wave orm; the resulting data points are then compiled and stored in the wave orm memory.
Horizontal Resolution – The smallest time increment that can be used to create wave orms; the minimum
requency.
Logic Signal Source – A type o signal generator that outputs digital patterns, such as a pulse or pattern
generator. Margin Testing – A common application in which a signal generator is used to stress components, devices
A type o analog modulation in which phase variations embed lower- requency in ormation into a carrier signal o higher requency: most commonly used in broadcast communications.
Megasamples per second (MS/s) – A sample rate unit equal to one million samples per second.
requency.
Memory Depth – The number o wave orm points used to create a record o a signal, which determines
between two xed voltage levels at regular intervals.
Substitution – A method used to develop a wave orm or use by a signal generator that involves creating
and/or modi ying a de ned signal to substitute or a signal rom unavailable circuitry.
Sweep Generator – A unction generator that can vary the requency o a signal, typically a sine wave,
over a speci ed time period.
Swept Sine Wave – A type o sine wave that increases in requency over some period o time. Timing Resolution – See Horizontal Resolution. Unit-under-test (UUT) – See device-under-test (DUT). Verifcation – A common application in which a signal generator is used to determine whether or not a
component, device or system operates as predicted, and con orms to industry standards. Vertical System – Within a signal generator, the system that denes the amplitude and o
Stimulus and acquisition instruments together make up a complete solution that can drive a device-under-test with complex real-world signals and acquire the resulting outputs. The oscilloscope is the industry-standard tool or acquisition. But only with a signal source can engineers really control what goes into the device. And that is o ten a necessity or making sense o what comes out o the device.
set level o the
output signal. Vertical Resolution – The smallest increment o voltage change that can be programmed in a signal
generator; the binary word width, in bits, o the instrument’s DAC, which de nes the amplitude accuracy and distortion o the reproduced wave orm.
the maximum amount o wave orm data (equivalent to time) that can be stored by an analog/mixed-signal Volt – The unit o electric potential di generator.
Summary Many engineers look at tasks like troubleshooting and design veri cation as purely “measurement” challenges, and tend to think automatically o their oscilloscope or logic analyzer as the whole solution. But these acquisition instruments have an important partner: the stimulus instrument – the signal source.
requency over some period o
Polarity – The direction in which current fows relative to its zero or ground level; usually re ers to the starting direction, positive or negative, o a wave orm.
Rise Time – Amount o time required or a pulse edge to make a transition to a state opposite its current level; in the case o rise time, rom low level to high level and, in the case o all time, rom high level to low level.
Megahertz (MHz) – 1,000,000 Hertz; a unit o
Frequency Sweep
erence in timing between two otherwise similar signals, also known as delay.
Phase Shi t Keying (PSK) – A type o digital modulation in which the carrier switches between two phase settings.
Digital-to-Analog Converter (DAC) – A digital electronic component that converts discrete binary values into an electrical signal.
Phase Modulation (PM)
Time placement o a cycle relative to a re erence wave orm or point in time.
Phase Shi t – The di
Digital Signal – A signal whose voltage samples are represented by discrete binary numbers.
or systems with impairments, such as jitter and timing violations, to deter-mine their operating limits, also known as stress testing.
A wave orm that increases in amplitude over some period o The number o times a ull wave orm cycle repeats in one time. second, measured in Hertz (Hz). Frequency equals 1 divided by period or wavelength. Phase
Amplitude
erence in timing between two otherwise similar signals; also known as phase shi t.
Device-under-test (DUT) – A device or measuring; synonymous with a unit-under-test (UUT).
Kilohertz (kHz) – 1,000 Hertz; a unit o
Frequency Modulation (FM)
A type o analog modulation in which requency variations embedded lower- requency in ormation into a carrier signal o higher requency: most commonly used in broadcast communications.
A wave orm with a ast rising edge, a width, and a ast alling edge. Rise Time
erence o the set-up voltage and actual output voltage.
increment o time by which an edge, cycle time, or pulse width can be changed.
50% Amplitude
90%
Arbitrary Wave orm Generator (AWG) – A type o analog/mixed-signal generator in which an output o the arbitrary analog signals created on memory is possible; a sophisticated play-back system that delivers wave orms based on stored digital data that describes the constantly changing voltage levels o an AC signal.
Delay – The di
Signal Source
Waveform points in memory
W a v e fo rm
a c c u m u a to r
Arbitrary – A wave orm dened by individual pre erence or convenience rather than by the intrinsic nature o the signal generator.
DC Accuracy – The di
ra te )
Clock (fixed rate)
Analog-to-Digital Converter (ADC) – A digital electronic component that converts continuous analog signals into proportional discrete binary (digital) values.
Data Pattern Generator – A type o signal generator that generates single or multiple streams o digital patterns; also known as a pattern generator or data generator.
e rm y r
M e m o
Direct Digital Synthesis (DDS) l lo ck Imagine all points o the wave orm in memory spread at equal angles around a C o u n te r W a v e f o rm ( signal ri leis ra te) generated by recalling points rom memory. M e m o ry
Analog Signal – A signal with continuously variable voltages.
Damped Sine Wave – A type o sine wave in which a circuit oscillates rom an impulse, and then winds down over time.
Captured Waveform
S a m p
Phase Modulation (PM) – A type o analog modulation in which phase variations embed lower- requency in ormation into a carrier signal o higher- requency; most commonly used in broadcast communications.
Amplitude Shi t Keying (ASK) – A type o digital modulation in which the digital modulating signal causes the output requency to switch between two amplitudes.
Clock Rate – See Sample Rate.
r t
re i ter
Phase – The amount o time that passes rom the beginning o a cycle to the beginning o the next cycle, measured in degrees.
Amplitude Modulation (AM) – A type o analog modulation in which amplitude variations embed lowerrequency in ormation into a carrier signal o higher- requency; most commonly used in broadcast communications.
Bandwidth – A requency range, usually limited by –3 dB.
In a
DAC
Waveform Memory
GPIB/LAN
y
Out
Wave orm Generation Principals
Sample Clock (variable rate)
r
Period – The amount o time it takes a wave to complete one cycle. The period equals 1/ requency.
Amplitude – The magnitude o a quantity or strength o a signal. In electronics, amplitude usually re ers to either voltage or power.
Arbitrary/Function Generator (AFG) – A type o analog/mixed-signal generator that produces stable wave orms in standard shapes.
Oscilloscope / Logic Analyser
Logic Sources: Outputs digital patterns such as pulses or patterns.
Aberration – Overshoot or undershoot in a wave orm.
erence.
Microsecond (µs) – A unit o time equivalent to 0.000001 seconds.
Voltage – The di
Millisecond (ms) – A unit o time equivalent to 0.001 seconds.
Wave – The generic term or a pattern that repeats over time. Common types include: sine, square,
Mixed Signal Generator – A type o signal generator, such as an arbitrary wave orm generator or arbitrary/
unction generator, that outputs both analog wave orms and digital patterns.
Modulated Signal – A signal in which amplitude, phase, and/or requency variations embed lower- requency
in ormation into a carrier signal o higher- requency. Nanosecond (ns) – A unit o time equivalent to 0.000000001 seconds. Noise – An unwanted voltage or current in an electrical circuit. O
set – DC component o a signal that contains both AC and DC values; voltage between circuit ground
and the center o a signal’s amplitude.
Pattern Generator – A type o logic signal source that generates the digital pattern o many channels;
erence in electric potential, expressed in volts, between two points.
rectangular, saw-tooth, triangle, step, pulse, periodic, non-periodic, synchronous, asynchronous.
Wave orm – A graphic representation o a wave’s activity and its variation over time.
Wave orm Point – A digital value that represents the voltage o a signal at a specic point in time,
calculated rom sample points and stored in memory.
