Band-Pass Filter on GNU Radio

2015 Implementation of Band-Pass filter

Author: Rakesh Email id: [email protected]

What is Gnu radio?

GNU Radio is a software library, which can be used to develop complete applications for radio engineering and signal processing. Introduction

GNU Radio is a free and open-source software development toolkit that provides signal processing blocks to implement software radios. It can be used with readilyavailable low-cost eternal R! hardware to create software-defined radios, or without hardware in a simulation-like environment. GNU Radio is licensed under the GNU General "ublic #icense $G"#% version &. 'll of the code is copyright of the !ree (oftware !oundation. )hile all the applications are implemented using python language while critical signal processing path is done using *++ language. Idea behind GNURADIO

he goal is to give ordinary software people the ability to hack the electromagnetic spectrum, i.e. to understand the radio spectrum and think of clever ways to use it. Wh GNURADIO

Instead of purchasing multiple epensive radios, a single generic radio can be imple implemen mented ted using using GNU Radio Radio softwa software re and with with suppor supportt of minim minimal al hardwa hardware re to receive and transmit processed signal at reuired freuencies and any data type can be passed from one block to another i.e.it can be in bits, bytes, vectors, bursts or more comple data types (ince the performanc performancee critical critical blocks are implemented implemented in *++ using processor processor floating point etensions the developers are able to implement real-time, high-throughput radio systems in a simple-to-use, rapid-application-development environment.

/01&, (hree #akshmi *omple, 2nd !loor, 3pp. o 4ivekananda "ark, Girinagar, 5angalore - 678896. "h. No: 898-27;22;27, )ebsite: www.tenettech.com www.tenettech.com,,
3ne can use it to write applications to receive data out of digital streams or to send data into digital streams, which is then transmitted using hardware. GNU Radio has filters, channel codes, synchronisation elements, euali>ers, demodulators, vocoders, decoders, and many other elements which are called as blocks that are typically found in radio systems. !eatures he main features of GNU Radio are fle!ibilit and confi"urabilit# <tending GNU Radio is also uite easy, if you find a specific block that is missing you can uickly create and add it.

What is Band-Pass filter?

' 5and-" 5and-"ass ass filte filterr is a device device that that passes passes freuencies with within in a cert certai ain n range range and and re?ec re?ects ts $attenuates% attenuates% freuencies outside that range. 'n eample of an analogue electronic 5and-"ass filter is an R#* circuit $a resistor@inductor@ capacitor circuit%. hese filters can also be created by combining a #ow-"ass filter with a high pass filter. 5and-"ass is an ad?ective that describes a type of filter or filtering processA it is to be distinguished from pass-band, which refers to the actual portion of affected spectrum. Bence, one might might say C' dual 5and-" 5and-"ass ass filter filter has two pass-b pass-bands andsC. C. ' 5and-"a 5and-"ass ss signal signal is a signal signal containing a band of freuencies not ad?acent to >ero freuency, such as a signal that comes out of a 5and-"ass filter. 'n ideal 5and-"ass filter would have a completely flat pass-band $e.g. with no gain1attenuation throughout% and would completely attenuate all freuencies outside the pass-band. 'dditionally, the transition out of the pass-band would be instantaneous in freuency. In practice, no 5and"ass filter is ideal. he filter does not attenuate all freuencies outside the desired freuency range completelyA in particular, there is a region ?ust outside the intended pass-band where freuencies are attenuated, but not re?ected. his is known as the filter roll-off, and it is usually epressed in d5 of attenuation per octave or decade of freuency. Generally, Generally, the design of a filter seeks to make the roll-off as narrow as possible, thus allowing the filter to perform as close as possible to its intended design. 3ften, this is achieved at the epense of pass-band or stop-band ripple. he bandwidth bandwidth of the filter filter is simply simply the differe difference nce betwee between n the upper and lower lower cutoff cutoff freuencies. he shape factor is the ratio of bandwidths measured using two different attenuation values to determine the cutoff freuency, e.g., a shape factor of 2:D at &81& d5 means the bandwidth measured between freuencies at &8 d5 attenuation is twice that measured between freuencies at & d5 attenuation. 3ptical 5and-"ass filters are common in photography and theatre lighting work. hese filters take the form of a transparent colored film or sheet. 5and-"ass filters are widely used in wireless transmitters and receivers. he main function of such a filter in a transmitter is to limit the bandwidth of the output signal to the band allocated

for the transmission. his prevents the transmitter from interfering with other stations. In a receiver, a 5and-"ass filter allows signals within a selected range of freuencies to be heard or decoded, while preventing signals at unwanted freuencies from getting through. ' 5and-"ass filter also optimi>es the signal-to-noise ratio and sensitivity of a receiver.

D% 5and 5and-" -"as asss filt filter er he GNU Radio *ompanion with basic blocks $3ptions block and 4ariable ariable block%

defines the IE, itle and Eescription of the eperiment. Options bloc$ defines

defines to declare variables globally. his block maps a value to a uniue %ariable %ariable Bloc$ defines variable. his variable block has no graphical representation. he v ariable can be referenced $by IE% from other blocks in the flowgraph. IE F samprate o 4alue F &2888B> o

&i"nal source is a wave form genrator. 4ery first block genrates the sine wave, second block genrates the suare wave, third block genrates triangler wave and finaly fourth block genrates the sawtooth waveform.

o

IE:analogsigsource8

o

3utput type: float

o

!re: D08B>

o

'mplitude: D4

Band-Pa Band-Pass ss filter' filter' this filter is a convenience wrapper for an fir filter. (ample rate, cutoff freency and transition width are in Bert>. IE: bandpassfilter8 ype: float #ow cutoff fre: 288B> Bigh cutoff fre: 988B>

(hrottel bloc$ : hrottel is a device that control the flow of samples such that average rate does not eceeds samples1sec. hrottle samples1sec. hrottle is used because no hardware interface h as done.

o o o

IE: blocksthrottel ype: float 4ec length: D

W) GUI scope sin$' he )H GUI (cope sink is the destination block of the flow chart. his block is used to view the time domain representation of the output. he simulation output of the received signal is seen with this block. IE: wguiscopesink28 o ype: float o

(he *omplete bloc$ representation

Genrated output


Band-Pass Filter on GNU Radio

Recommend Documents