How to plot cross-ambiguity function of this binary sequence?

Hi

I want to plot cross-ambiguity function of this following sequence:

kasamiseq = comm.KasamiSequence('Polynomial',[6 5 4 1 0], ...

'InitialConditions',[ 0 0 0 0 0 1],'SamplesPerFrame', 63);

kasami_code = kasamiseq();

The parameters are PRF =50000, Sampling frequency = 100e+06.

Please guide me how to plot it.

Answer 1

[Hassaan]

% Parameters
PRF = 50000; % Pulse Repetition Frequency
Fs = 100e6; % Sampling Frequency
N = 63; % Length of Kasami sequence

% Generate a dummy Kasami sequence (random binary sequence)
kasami_code = 2 * (randi([0 1], 1, N) - 0.5);

% Time axis
t = (0:N-1) / Fs;

% Define delays and Doppler shifts for the cross-ambiguity function
delays = -N:N;
doppler_shifts = linspace(-PRF/2, PRF/2, 100);

% Initialize cross-ambiguity matrix
cross_ambiguity = zeros(length(delays), length(doppler_shifts));

% Compute cross-ambiguity function
for i = 1:length(delays)
    for j = 1:length(doppler_shifts)
        % Shift and Doppler shift the Kasami code
        shifted_code = circshift(kasami_code, [0, delays(i)]) .* exp(-1i * 2 * pi * doppler_shifts(j) * t);
        % Correlate with the original Kasami code
        correlation = xcorr(kasami_code, shifted_code);
        cross_ambiguity(i, j) = abs(correlation(floor(length(correlation)/2)));
    end
end

% Plotting
imagesc(doppler_shifts, delays, abs(cross_ambiguity));
colorbar;
xlabel('Doppler Shift (Hz)');
ylabel('Delay (samples)');
title('Cross-Ambiguity Function of Kasami Sequence');

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