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

frequencyplotsignal processing

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

Best Answer

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.

Related Solutions

MATLAB: Memory leak from waveform plotting at high frequency

I don’t see the problem.

f = (200 : 0.5 : 245)*1E+6;
t = 0 : 0.01 : 1; 
y = sin (2 * pi .* f(:) * t);
whos y
    Name       Size             Bytes  Class     Attributes
    y         91x101            73528  double

A 73.528 kB array isn’t that large.

MATLAB: Return X coordinate of a fft plot where 80% of the total area under the curve is achieved

Try this:

t = linspace(0, 10, 150);                                   % Create Data

y = sin(2*pi*t*3) .* cos(2*pi*t*2) + 0.01*randn(size(t));   % Create Data
L = numel(t);
Ts = mean(diff(t));                                         % Sampling Interval
Fs = 1/Ts;                                                  % Sampling Frequency
Fn = Fs/2;                                                  % Nyquist Frequency
FTy = fft(y)/L;                                             % Fourier Transform
Fv = linspace(0, 1, fix(L/2)+1)*Fn;                         % Frequency Vector
Iv = 1:numel(Fv);                                           % Index Vector
areaFrac = 0.8;                                             % Desired Fraction Of Total Area
areaTot = trapz(Fv, abs(FTy(Iv)));                          % Total Area
areaCum = cumtrapz(Fv, abs(FTy(Iv)));                       % Cumulative Integral
Fv80 = interp1(areaCum, Fv, areaTot*areaFrac, 'spline')     % Frequency Corresponding To 80% Total Area
FTy80 = interp1(Fv, abs(FTy(Iv))*2, Fv80, 'spline')         % Value of Fourier Transform At ‘Fv80’
figure
plot(Fv, abs(FTy(Iv))*2, '-b')
hold on
plot(Fv, areaCum, '-k')
plot([0 max(Fv)], [1 1]*areaTot, '--k')
plot([0 max(Fv)], [1 1]*areaFrac*areaTot, ':k')
plot([1 1]*Fv80, [0 FTy80], '-r')
plot(Fv80, areaTot*areaFrac, 'r+')
hold off
legend('Fourier Transform', 'Cumulative Area', 'Maximum Area', '80% Maximum Area', 'Fourier Transform at 80% Maximum Area')

Experiment to get the result you want.

Best Answer

Related Solutions

MATLAB: Memory leak from waveform plotting at high frequency

MATLAB: Return X coordinate of a fft plot where 80% of the total area under the curve is achieved

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