plot frequency/amplitude response of data from labview

hi

i have exported data from labview to plot them in matlab.i tried but it dose not give me same plot as labview can anyone help please i have attached my data.

[Star Strider]

It does not give me anything resembling that plot with my code, either. Ther are a few similarities, but certainly no match.

Can you also provide a time vector? I would like to check to see if the data are regularly sampled, and I would like to know the sampling frequency.

[shirin]

thanks for your reply. the sampling frequency is 2.5GHz. and the data are 32768 samples.

regards

[Star Strider]

I’ve worked with this on and off during the day, and I have no idea why the LabView and MATLAB spectra for that signal are so different. LabView must be doing something to it that it’s not telling you.

My code:

[D,S] = xlsread('shirin test.xlsx');
L = numel(D);
Fs = 2.5E9;                                                         % Sampling Frequency
t = linspace(0, L, L)*1/Fs;                                         % Create Time Vector
Fn = Fs/2;                                                          % Nyquist Frequency
FTD = fft(D)/L;                                                     % Scaled Fourier Transform
Fv = linspace(0, 1, fix(L/2)+1)*Fn;                                 % Frequency Vector
Iv = 1:numel(Fv);                                                   % Index Vector

figure
plot(Fv, 20*log10(abs(FTD(Iv))*2))
grid
xlim([0  2E+8])

If you can find out what LabView is doing or how it calculates the Fourier transform that makes it so different from the MATLAB result, please post back here.