band-pass filter on gnu radio

8/9/2019 Band-Pass Filter on GNU Radio

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2015

Author: Rakesh

Email id: [email protected]

Implementation of Band-Pass filter


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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 readily-

available low-cost eternal 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 ofthe 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 epensive radios, a single generic radio can be

implemented using GNU Radio software and with support of minimal hardware to

receive and transmit processed signal at reuired freuencies 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 performance critical blocks are implemented in *++ using processor floating

point etensions 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,


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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, euali>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!ibilitand confi"urabilit#


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What is Band-Pass filter?

' 5and-"ass filter is a device that passes freuencieswithin a certain range and re?ects

$attenuates% freuencies outside that range.

'n eample 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 say C' dual 5and-"ass filter has two pass-bandsC. ' 5and-"ass signal is a signal

containing a band of freuencies not ad?acent to >ero freuency, 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 freuencies outside the pass-band. 'dditionally,

the transition out of the pass-band would be instantaneous in freuency. In practice, no 5and-

"ass filter is ideal. he filter does not attenuate all freuencies outside the desired freuency

range completelyA in particular, there is a region ?ust outside the intended pass-band where

freuencies are attenuated, but not re?ected. his is known as the filter roll-off, and it is usually

epressed in d5 of attenuation per octave or decade of freuency. 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 epense of pass-band or stop-band

ripple.

he bandwidth of the filter is simply the difference between the upper and lower cutoff

freuencies. he shape factor is the ratio of bandwidths measured using two different attenuation

values to determine the cutoff freuency, e.g., a shape factor of 2:D at &81& d5 means the

bandwidth measured between freuencies at &8 d5 attenuation is twice that measured between

freuencies 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




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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 freuencies to be heard or

decoded, while preventing signals at unwanted freuencies from getting through. ' 5and-"ass

filter also optimi>es the signal-to-noise ratio and sensitivity of a receiver.




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D% 5and-"ass filter

he GNU Radio *ompanion with basic blocks $3ptions block and 4ariable block%

Options bloc$defines the IE, itle and Eescription of the eperiment.




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%ariable Bloc$defines to declare variables globally. his block maps a value to a uniue

variable. his variable block has no graphical representation. he variable can be referenced

$by IE% from other blocks in the flowgraph.

o IE F samprate

o 4alue F &2888B>

&i"nal sourceis a wave form genrator. 4ery first block genrates the sine wave, second block

genrates the suare wave, third block genrates triangler wave and finaly fourth block genrates the

sawtooth waveform.

o IE:analogsigsource8

o 3utput type: float

o !re: D08B>

o 'mplitude: D4




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Band-Pass filter' this filter is a convenience wrapper for an fir filter. (ample rate, cutoff

freency and transition width are in Bert>.

IE: bandpassfilter8

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 doesnot eceeds samples1sec.hrottle is used because no hardware interface has done.

o IE: blocksthrottel

o ype: float

o 4ec length: D




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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.

o IE: wguiscopesink28

o ype: float




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band-pass filter on gnu radio

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