MATLAB: Plot Signals A & B, Combined Y, and Y with Gaussian Noise Using Subplot

lot two signals (A and B) sampled at 1 kHz for 100 ms, their combination Y = A + B, and Y with added white Gaussian noise (variance = 2), using subplots.

Key MATLAB Steps:

1. Define sampling: fs = 1000; t = 0:1/fs:0.1-1/fs; (100 samples).
2. Create signals: e.g., A = sin(2*pi*50*t); B = 0.7*sin(2*pi*200*t);.
3. Combine: Y = A + B;.
4. Add noise: Y_noisy = Y + sqrt(2)*randn(size(t)); (variance = 2).
5. Use figure and subplot(3,1,...):
   • Top: Plot A and B (different colors/styles).
   • Middle: Clean Y.
   • Bottom: Noisy Y.
6. Add grid on, titles, labels (time in ms), and legend.

   % Parameters
   fs = 1000;          % Sampling frequency: 1 kHz
   T = 0.1;            % Total time: 100 ms
   t = 0:1/fs:T-1/fs;  % Time vector (100 samples)

   % Signal A: Example - 50 Hz sine wave
   A = sin(2*pi*50*t);

   % Signal B: Example - 200 Hz sine wave
   B = 0.7 * sin(2*pi*200*t);

   % Combined signal Y = A + B
   Y = A + B;

   % Add white Gaussian noise with variance 2 (standard deviation = sqrt(2) ≈ 1.414)
   noise = sqrt(2) * randn(size(t));   % White Gaussian noise with variance 2
   Y_noisy = Y + noise;

   % Create figure with subplots
   figure('Name', 'Signal Plotting', 'NumberTitle', 'off');

   % Subplot 1: Original signals A and B
   subplot(3,1,1);
   plot(t*1000, A, 'b', 'LineWidth', 1.5); hold on;
   plot(t*1000, B, 'r--', 'LineWidth', 1.5);
   grid on;
   title('Signal A (blue) and Signal B (red)');
   xlabel('Time (ms)');
   ylabel('Amplitude');
   legend('A (50 Hz)', 'B (200 Hz)');
   hold off;

   % Subplot 2: Combined signal Y = A + B (clean)
   subplot(3,1,2);
   plot(t*1000, Y, 'g', 'LineWidth', 1.5);
   grid on;
   title('Combined Signal Y = A + B (clean)');
   xlabel('Time (ms)');
   ylabel('Amplitude');

   % Subplot 3: Combined signal Y with white Gaussian noise (variance = 2)
   subplot(3,1,3);
   plot(t*1000, Y_noisy, 'k', 'LineWidth', 1.2);
   grid on;
   title('Signal Y with White Gaussian Noise (variance = 2)');
   xlabel('Time (ms)');
   ylabel('Amplitude');

   % Adjust layout
   sgtitle('Bidirectional AC-DC Converter Control Signals Simulation Example');
   set(gcf, 'Position', [100 100 900 600]);   

   What this code does:

   • Samples two example signals (50 Hz and 200 Hz sine waves) at 1 kHz for 100 ms.
   • Combines them into Y = A + B.
   • Adds white Gaussian noise with variance = 2 to Y.
   • Uses three subplots:
     1. Original signals A and B.
     2. Clean combined signal Y.
     3. Noisy version of Y.
   • Time axis in milliseconds for clarity.