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Dayananda Sagar College of EngineeringCenter for Post Graduation Studies
Department of Electronics and Communications Engineering
Project Seminar MTech Project Phase 3
Project Title : EVALUATION OF POLYPHASE FFTARCHITECTURE FOR PULSE DETECTION AND MEASUREMENT
Student Name : JEEVITHA T (1DS12LEC06)
Internal Project Guide: External Project Guide:Prof. Kiran Gupta Hemanth Vasant ParanjapeECE dept,DSCE Scientist E, DARE,DRDO
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Problem statement
Time of Arrival(TOA) PDW parameter that assigns a time tag to the leading edge of
a received pulse at the receiver input.
For a digital EW receiver, the spectrum estimator (normally an FFT) is usually
the limiting factor in update rate due to its computational complexity.
update rate 1/ frequency resolution.
Consider a monobit receiver:
256 samples at 2.56GHz TOA resolution 100ns.
with 50% overlap at the same Fs TOA resolution 50ns
increasing the number of FFTs.
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Phase 1 ReviewPhase 1 Review
Receiver considered is a Multi-bit Electronic Warfare Receiver
Receiver consists of a decimation filter and FFT block along with an encoder thatoutputs the PDW(Pulse Descriptor Words).
The shaded block is realized as a polyphase DFT which uses decimation in frequencydomain.
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objective
the proposed method to increase the TOA resolution is to use decimation in the
frequency domain.
implement the decimation in frequency domain through a channelised polyphase
filtering method.
incorporate the channelised polyphase filtering method in the receiver model.
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Frequency Channelization
Filter bank:
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Polyphase Structure for FFT filter bank
USN: 1DS12LEC06 6
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Decimation filter design process:
STAGE 1: FFT filter bank
rectangular window in time domain sinc function in frequency domain
filter shape is not desirable
sidelobes are very high
Weighing function can be used in time domain
the detailed response of the single filter and the filter bank is as shown
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USN: 1DS12LEC06 8
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Continued..
STAGE 2 : Decimated FFT filter BankALGORITHM: Decimation in Frequency Domain:
Step 1:
Step 2:
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Step 4:
Step 5:
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Step 6:
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Results:
USN: 1DS12LEC06 13
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Continued..
Stage 3: Windowed Decimated FFT filter Bank
To widen the individual filters and also suppress the sidelobes a window is appliedto the input data.
The corresponding effect in the frequency domain is the wide bandwidth of eachindividual filter shape in the filter bank.
ALGORITHM:
Step 1:
Step 2:
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Continued..
Step 3:
Step 4: 32 point FFT is performed on these y values , 16 individual filters aregenerated.
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Window function generated using an FDATOOL
Design Parameters:
N=256; M=8; 1= 0.01; 2=0.001; fs=3000MHz;Fp =fs/(N/M) ; Fs = 2*Fp;
USN: 1DS12LEC06 16
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Continued..
Step 1:
Step 2:
Park Mc- Clellans Criteria:
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Advantages of Polyphase Filtering
First, by parallelizing the filter through polyphase decomposition, the sampling rate of
each individual filter is reduced by a factor of 1 /D, where D is the number of filters.
A second significant advantage to using the channelized polyphase filtering
method is an increase in time resolution, which improves the TOA and PW calculations
in an EW receiver.
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Comparison:
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Remaining Work:
incorporate the filter designed into the receiver model
Generate the test signals
perform various processing such as:
Deinterleaving
PRI generation
Tracking
PDW generation
GUI design in MATLAB.
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MATLAB simulation
Generation of the input signals:
FILE NAME DESCRIPTION
Known_pattern.m Accepts the number of pulses transfers the control test_case_generator.
Outputs the details of the input info.txt
Test_case_pattern.m Provides the user a platform to enter the details of the inputpattern.Transfers the control to cw_generator.m depending on theuser entries.
Cw_generator.m Used to generate cw pulses.
Info.txt Contains the details of the input signal.
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COMPLETE_MODEL.M ALGORITHM
1. The input data/ samples are stored in samples.txt
2. Grouping of the data begins :P = length(A);P = P - mod(P,256);L = (P/N);
where A is a variable which contains the imported data (samples.txt)
3. Design an equiripple low pass FIR filter with the following parameters: Fs=1350MHz Fp=21.09375MHz Fs=42.1875MHz Wp=1/64 Ws=1/32
Fdatool is used to generate the filter co-efficients.
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Samples(14080)
L21
1 2 3256
P= P- mod(P,256) Mod(x,y)= x-n.*yn = floor(x./y)
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Continued.
4. Decimation in the frequency domain is applied on the incoming data:
Let x(n) be the input, h(n) be the filter co-efficients :
5. Calculate the 32 point FFT of the processed data.
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Peak detection:
6. Calculate the first peak(maximum) using
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Continued
THANK YOU