How can I get a time versus amplitude graph from the waveform.

Question

Vahram Voskerchyan 2021-10-23

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1570188-how-can-i-get-a-time-versus-amplitude-graph-from-the-waveform

回答： Star Strider 2021-10-23

I have used the following code to get a FMCW sweep for ThZ range.

sFMCW = phased.FMCWWaveform('SweepBandwidth',192e12,...
    'SweepTime',1e-9,...
   'SampleRate',384e12,'SweepDirection','Triangle',...
   'NumSweeps',2);
sig = step(sFMCW);
windowlength = 32;
noverlap = 16;
nfft = 32;
spectrogram(sig,windowlength,noverlap,nfft,sFMCW.SampleRate,'yaxis')

And got the following graph.

How can I get time versus amplitude of the following graph?

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Answer 1

Star Strider 2021-10-23

1
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1570188-how-can-i-get-a-time-versus-amplitude-graph-from-the-waveform#answer_814933

The spectrogram function returns amplitude (the ‘z’ axis of the rotated surf plot) in units of dB/Hz, so it will not produce the amplitude results that the fft function would return.

Instead, use the pspectrum function with the 'spectrogram' option, that will return the amplitude uints (again the ‘z’ axis of the rotated surf plot) of the original signal.

Compare the two funcitons with the same signal to see the difference in the results. Both of them provide the ability to get the data directly from the outputs without having to recover them from the surf plot (although that is always an option).

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