Underwater Target Detection with an Active Sonar System

Fairly new to MATLAB, there is guidance on Underwater Target Detection wiith and Active Sonar System available - just want to understand where to appropriately construct the script and how to generate the graphs and visuals?

Answer 1

[Diwakar Diwakar]

This code snippet that demonstrates a simple target detection scenario using an active sonar system in MATLAB. This example uses a basic approach with pulse transmission, echo reception, and thresholding for detection.

% Sonar system parameters
transmitFreq = 20000;        % Transmit frequency in Hz
pulseWidth = 10e-3;          % Pulse width in seconds
samplingFreq = 100e3;        % Sampling frequency in Hz
soundSpeed = 1500;           % Speed of sound in water in m/s

% Target properties
targetRange = 100;           % Target range in meters
targetStrength = 0.8;        % Target strength (amplitude of echo)

% Signal generation
t = 0:1/samplingFreq:pulseWidth;  % Time vector for pulse
pulse = cos(2*pi*transmitFreq*t); % Generated pulse

% Signal propagation modeling
propagationDelay = 2 * targetRange / soundSpeed;  % Two-way propagation delay
receivedSignal = [zeros(1, round(samplingFreq * propagationDelay)), targetStrength * pulse];

% Matched filtering
correlation = conv(receivedSignal, fliplr(pulse));

% Detection thresholding
threshold = 0.5 * max(correlation);  % Set detection threshold as half of the maximum correlation
detections = find(correlation > threshold);

% Plotting
figure;
subplot(2,1,1);
plot(t, pulse);
xlabel('Time (s)');
ylabel('Amplitude');
title('Transmitted Pulse');

subplot(2,1,2);
timeAxis = (0:length(receivedSignal)-1) / samplingFreq;
plot(timeAxis, receivedSignal);
hold on;
plot(timeAxis, correlation);
stem(detections / samplingFreq, correlation(detections), 'r', 'Marker', 'x');
hold off;
xlabel('Time (s)');
ylabel('Amplitude');
legend('Received Signal', 'Correlation', 'Detections');
title('Received Signal and Correlation');

In this example, we define the parameters for the sonar system, including transmit frequency, pulse width, sampling frequency, and speed of sound in water. We then generate a pulse signal and simulate the signal propagation by adding a delay to the received signal. The received signal is processed using matched filtering, and a detection threshold is applied to identify potential target detections. Finally, the transmitted pulse and the received signal with correlation and detected targets are plotted using the subplot function.