Capturing FFT from TDS Oscilloscope with MATLAB Code

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Michael Cimorelli 2017-12-21

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https://ww2.mathworks.cn/matlabcentral/answers/374135-capturing-fft-from-tds-oscilloscope-with-matlab-code

编辑： Michael Cimorelli 2017-12-21

I have a code shown below that can capture voltage versus time data and then calculate the spectrogram for the system I am working with... I am trying to read/store the FFT directly from the oscilloscope and having difficulty finding anything on Tektronix website or their support...

I am trying to replicate an old paper (which shows them capture the data directly from the scope). I can FFT the data myself and get a matching curve, but I would like to capture it directly from the scope.

%%Instrument Connection
clear all; close all; clc;
% Create a VISA-USB object.
resourceName = instrfind('Type', 'visa-usb', 'RsrcName', 'USB0::0x0699::0x0363::C054303::0::INSTR', 'Tag', '');
% Create the VISA-USB object if it does not exist
% otherwise use the object that was found.
if isempty(resourceName)
    resourceName = visa('NI', 'USB0::0x0699::0x0363::C054303::0::INSTR');
else
    fclose(resourceName);
    resourceName = resourceName(1);
end
% Create a device object . 
scope = icdevice('tektronix_tds2000B.mdd', resourceName);
%%Section 1
% Channel 1 is used to capture the BACKGROUND
clc; 
disconnect(scope);
connect(scope);
devicereset(scope);
set(scope.Channel(1), 'Scale', 20);
set(scope.Channel(1), 'Coupling', 'ac');
set(scope.Channel(1), 'Probe', 1.0);
set(scope.Trigger(1), 'Coupling', 'ac');
set(scope.Trigger(1), 'Source', 'channel1');
set(scope.Trigger(1), 'Level', 0.40);
set(scope.Display(1), 'Format', 'yt');
set(scope.Display(1), 'Persistence', 0.0);
set(scope.Acquisition(1), 'Timebase', 2.5E-06);
set(scope.Acquisition(1), 'Delay', 12.5e-6);
set(scope.Trigger(1), 'Mode', 'auto');
disconnect(scope);
%%Section 2 
% Graphing the BACKGROUND and incoming Fast FFT 
clc;
disconnect(scope);
connect(scope);
scopeTrigger = get(scope,'trigger');
invoke(scopeTrigger, 'trigger');
[Y, X, YUNIT, XUNIT] = invoke(get(scope, 'Waveform'), 'readwaveform', 'channel1');
disconnect(scope);
close all;
plot(X,Y);
xlabel('Time (us)');
ylabel('Voltage (V)');
axis([0 2.5e-5 -6 6]) % Time in us and Volts in V
figure(2)
spectrogram(Y,kaiser(256,2),240,1280,1E8);
ax = gca;
ax.XLim = [0.3,5]; % Frequency range in MHz
ax.YLim = [0,25]; % Time range in us
[S,F,T] = spectrogram(Y,kaiser(256,2),240,1280,1E8); % Storing as a vector
figure(3)
Fs = 1e8;             % Sampling frequency                    
T = 1/Fs;             % Sampling period       
L = 2500;             % Length of signal
t = (0:L-1)*T;        % Time vecto
FT = fft(Y);
P2 = abs(FT/L);
P1 = P2(1:L/2+1);
P1(2:end-1) = 2*P1(2:end-1);
f = Fs*(0:(L/2))/L;
plot(f,P1) 
title('Single-Sided Amplitude Spectrum of X(t)')
xlabel('f (Hz)')
ylabel('|P1(f)|')