MATLAB: I have an excel data of time vs voltage plot of a signal and have to plot a fft for the same. the excitation frequency is 50khz, but the fft peak is arriving at 35khz. how do i fix this

fft

the matlab code is mentioned below
if true
  % code
end
[D,T] = xlsread('50KHZ.xlsx');
F = D(:,2);                 % Data Channel
Ts = 8e-4;                  % Sampling Interval (s)
Fs = 1/Ts;                  % Sampling Frequency (Hz)
Fn = Fs/2;                  % excitation Frequency
LF = size(F,1);             % Length of Data Vector
T = linspace(0,1,LF)*Ts;    % Create Time Vector
figure(1)                   % Plot Data 
plot(T, F)
grid
xlabel('Time')
ylabel('Voltage')
FF = fft(F)/LF;             % Fourier Series of Data, Freq Vector
Fv = linspace(0,1,fix(LF/2)+1)*Fn;
Iv = 1:length(Fv);          % Index Vector
figure(2)                   % Plot FFT
plot(Fv, abs(FF(Iv)))
grid
xlabel('Frequency (Hz)')
ylabel('Amplitude')

Best Answer

I recognise that code (thank you for quoting it). The only problem may be that your sampling interval, ‘Ts’ is incorrect.
Assuming that ‘D(:,1)’ is your time vector (I don’t know if it is), see if changing the ‘Ts’ assignment to:
Ts = mean(diff(D(:,1)));    % Sampling Interval (s)
produces the correct plot.
If ‘D(:,1)’ is your time vector, also change the ‘T’ assignment to:
T = D(:,1);
NOTE — This is obviously UNTESTED CODE. I don’t see any typographical errors.
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