pcoff.m

％ This program calculates radar ranges in a jamming environment. It works ％ with both Stand-off jam

% PULSE COMPRESSION WAVEFORM WITH FREQUENCY OFFSET
% ------------------------------------------------

clear;clf;clc;

% Input Chirp Bandwidth,Pulsewidth and Offset Frequency

bw=1e6;		% Bandwidth - Hz
T= 1e-4; 	% Pulsewidth - sec
fo=2e5;     % Frequency Offset - Hz

%Input FFT Points

lfft=1024;

% Set Time Base 

t=-T/2:T/(lfft-1):T/2;

% Sample Complex Chirp

s= exp(-j*pi*bw*t.*t/T);

% Find Fourier Spectrum of Chirp

ZY= fft(s,lfft);
Y=fftshift(ZY);

% Find Chirp Power Spectral Density

Psd=Y.*conj(Y)/lfft;
A=ceil(max(Psd));
l=length(Y);
f=(1/T)*(-(l-1)/2:(l-1)/2);

% Find Matched Filter Chirp Time Waveform

zh=ifft(Psd,lfft);
h=fftshift(zh);

% Input Frequency Offset Signals

s1=exp(-j*2*pi*fo*t)+exp(j*2*pi*fo*t);
so=s.*s1;

% Find Fourier Spectrum of Offset

ZZY=fft(so,lfft);
YY=fftshift(ZZY);

% Find Power Spectral Density of Offset

Psd1=YY.*conj(Y)/lfft;

% Find Offset Matched Filter Time Waveform

zzh=ifft(Psd1,lfft);
hh=fftshift(zzh);

% Plot Time Waveform

plot(t,abs(h),t,abs(hh));grid;
axis([-T/4 T/4 0 1 ]);
title(['PC Matched Filter Output']);
xlabel('Time - Sec');ylabel('Amplitude');
text(.2e-5,.95,'No Offset');
text(-2.4e-5,.85,'Repeater With Offset Frequency');
text(.4e-5,.85,'Repeater With Offset Frequency');