Combine a waveform from a set of sine waves which are linearly increasing in frequency

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Nathan Kennedy 2017-11-2

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https://ww2.mathworks.cn/matlabcentral/answers/364748-combine-a-waveform-from-a-set-of-sine-waves-which-are-linearly-increasing-in-frequency

评论： Star Strider 2017-11-3

采纳的回答： Star Strider

在 MATLAB Online 中打开

Hi,

I generate and plot multiple waveforms which have increasing frequency. I want to combine them at each time interval of t, but how? Please share if you know how...

for f = 1:1:200  % Upto 200 Hz
t=[0 : 0.01 : 1]  
y=sin (2 * pi .* f .* t);
hold on
plot (t,y)
end

thanks

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采纳的回答

Star Strider 2017-11-2

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/364748-combine-a-waveform-from-a-set-of-sine-waves-which-are-linearly-increasing-in-frequency#answer_289097

在 MATLAB Online 中打开

Try this:

t = 0 : 0.01 : 1;
for f = 1:1:200  % Upto 200 Hz
    y(f,:) = sin (2 * pi .* f .* t);
end
plot (t,y)
hold on
plot(t, sum(y), ':r', 'LineWidth',2.5)
hold off

The sum is essentially zero for all columns.

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Nathan Kennedy 2017-11-3

The comment about fft is something I would like to add in

Star Strider 2017-11-3

在 MATLAB Online 中打开

You will find this documentation for the fft (link) function helpful.

Example —

t = 0 : 0.01 : 1;
for f = 1 : 2  % Upto 2 Hz
    y(f,:) = sin (2 * pi .* f .* t);
end
figure(1)
plot(t,y)
hold on
plot(t, sum(y), ':r', 'LineWidth',2.5)
hold off
L = length(t);                                          % Signal Length
Ts = t(2) - t(1);                                       % Sampling Time Interval
Fs = 1/Ts;                                              % Sampling Frequency
Fn = Fs/2;                                              % Nyquist Frequency
Fv = linspace(0, 1, fix(L/2)+1)*Fn;                     % Frequency Vector
Iv = 1:length(Fv);                                      % Index Vector
Fourier = fft(y, [], 2)/L;                              % Fourier Transform (Along Rows Of Matrix)
figure(2)
subplot(2,1,1)
plot(Fv, abs(Fourier(:,Iv))*2)
title('Amplitude')
grid
subplot(2,1,2)
plot(Fv, angle(Fourier(:,Iv)))
title('Phase')
xlabel('Frequency')
grid