PAM modulation problem with matlab

can anyone help me with this?

Answer 1

[Saurav]

Hi @mahdi nadimi,

I see that you need help in modulating a signal in MATLAB using PAM modulation.

Here’s a step-by-step guide to generate and plot a PAM modulated signal for any given binary sequence using MATLAB:

1. Define the Binary Sequence:

• Start with the binary sequence you want to modulate, e.g., ‘001001111110’.

2. Create an Encoding Map:

• Use a mapping to convert binary pairs to amplitude values, for example:

‘00’ → ‘-2’

‘11’ → ‘5’

‘01’ → ‘2’

‘10’ → ‘-5’

This mapping can be implemented using a ‘containers.Map’ in MATLAB.

Refer the following documentation to learn more about ‘containers.Map’:

https://www.mathworks.com/help/matlab/ref/containers.map.html

3. Initialize the Signal:

• Prepare an empty array to store the modulated signal values.
• Define the duration for each pulse, e.g., 300 samples.

4. Decode the Binary Sequence:

• Iterate through the binary sequence in steps matching the number of bits used per encoding unit.
• For each encoding unit, use the encoding map to find the corresponding amplitude.
• Append the amplitude value to the signal array, repeated for the pulse duration.

5. Plot the Modulated Signal:

• Create a time vector corresponding to the length of the modulated signal.
• Use the “plot” function to display the signal.

By following these steps, a PAM modulated signal can be effectively generated and visualized using MATLAB for any given binary sequence with a custom encoding scheme.

Here's an example of how this can be implemented in MATLAB:

% Define the binary sequence
binary_sequence = '001001111110';

% Define the mapping based on the given encoding scheme
encoding_map = containers.Map({'01', '10', '11', '00'}, [2, -5, 5, -2]);

% Initialize the signal array
signal = [];

% Pulse duration
pulse_duration = 300;

% Iterate through the binary sequence in steps of 2 to decode
for i = 1:2:length(binary_sequence)
    % Extract the current binary pair
    pair = binary_sequence(i:i+1);
    
    % Map the binary pair to its corresponding value
    modulated_value = encoding_map(pair);
    
    % Append the modulated value to the signal array for the pulse duration
    signal = [signal, repmat(modulated_value, 1, pulse_duration)];
end

% Plot the modulated signal
t = 1:length(signal);
figure;
plot(t, signal, 'LineWidth', 2);
xlabel('Time');
ylabel('Amplitude');
title('PAM Modulated Signal');
grid on;
axis tight;

Hope this helps.