Sine wave with variable frequency

I would like to create a sine wave with frequency changing every 2*T. Can someone help please.

Answer 1

[Manikanta Aditya]

Hi @Alhassane Sylla,

You can create a sine wave with a variable frequency in MATLAB by defining a time vector and then adjusting the frequency at intervals of 2*T. Here's an example of how you can achieve this:

% Define parameters
T = 1; % Base period
fs = 1000; % Sampling frequency
t = 0:1/fs:10*T; % Time vector for 10 periods

% Initialize the sine wave
y = zeros(size(t));

% Define the frequency change interval
interval = 2 * T;

% Loop through the time vector and change frequency every 2*T
for i = 1:length(t)
    if mod(t(i), interval) < T
        f = 1; % Frequency for the first T seconds
    else
        f = 2; % Frequency for the next T seconds
    end
    y(i) = sin(2 * pi * f * t(i));
end

% Plot the sine wave
figure;
plot(t, y);
xlabel('Time (s)');
ylabel('Amplitude');
title('Sine Wave with Variable Frequency');
grid on;

You can adjust the frequencies and the interval as needed. This code will generate a sine wave where the frequency changes every 2*T seconds.

I hope this will help you understand better, Thanks!

[Alhassane]

Hi Manikanta Aditya,

Thanks for your answer. I needed to change at every 2*T of time the frequency from 1 to 800k. Can you help with that?

[Manikanta Aditya]

Check this:

% Define parameters
T = 1; % Base period
fs = 1000000; % Sampling frequency (1 MHz) to accommodate high frequency
t = 0:1/fs:10*T; % Time vector for 10 periods

% Initialize the sine wave
y = zeros(size(t));

% Define the frequency change interval
interval = 2 * T;

% Loop through the time vector and change frequency every 2*T
for i = 1:length(t)
    if mod(t(i), interval) < T
        f = 1; % Frequency for the first T seconds
    else
        f = 800000; % Frequency for the next T seconds
    end
    y(i) = sin(2 * pi * f * t(i));
end

% Plot the sine wave
figure;
plot(t, y);
xlabel('Time (s)');
ylabel('Amplitude');
title('Sine Wave with Variable Frequency');
grid on;

●

[Alhassane]

Thank you Manikanta Aditya.