In a partially unknown system, I measured a square-wave signal as input and the associated system response. Now I would like to use fft() to determine the transfer function or the Bode diagram. I have attached the measurements. I have the following code (also from this forum) but it results in this very bad bode plot. where is my mistake?
input = x3bzeit((23000:39000),2);
output = x3bzeit((23000:39000),3);
time = x3bzeit((23000:39000),1)*10^(-6);

Fs = 1/mean(diff(time)); % Sampling Frequency
Fn = Fs/2; % Nyquist Frequency
L = numel(time);
FTinp = fft(input)/L;
FTout = fft(output)/L;
TF = FTout ./ FTinp; % Transfer Function
Fv = linspace(0, 1, fix(L/2)+1)*Fn; % Frequency Vector
Iv = 1:numel(Fv); % Index Vector
figure
subplot(2,1,1)
plot(Fv, 20*log10(abs(TF(Iv))))
set(gca, ‘XScale’, ‘log’)

title(‘Amplitude’)
ylabel(‘dB’)
subplot(2,1,2)
plot(Fv, angle(TF(Iv))*180/pi)
title(‘Phase’)
ylabel(‘°’)In a partially unknown system, I measured a square-wave signal as input and the associated system response. Now I would like to use fft() to determine the transfer function or the Bode diagram. I have attached the measurements. I have the following code (also from this forum) but it results in this very bad bode plot. where is my mistake?
input = x3bzeit((23000:39000),2);
output = x3bzeit((23000:39000),3);
time = x3bzeit((23000:39000),1)*10^(-6);

Fs = 1/mean(diff(time)); % Sampling Frequency
Fn = Fs/2; % Nyquist Frequency
L = numel(time);
FTinp = fft(input)/L;
FTout = fft(output)/L;
TF = FTout ./ FTinp; % Transfer Function
Fv = linspace(0, 1, fix(L/2)+1)*Fn; % Frequency Vector
Iv = 1:numel(Fv); % Index Vector
figure
subplot(2,1,1)
plot(Fv, 20*log10(abs(TF(Iv))))
set(gca, ‘XScale’, ‘log’)

title(‘Amplitude’)
ylabel(‘dB’)
subplot(2,1,2)
plot(Fv, angle(TF(Iv))*180/pi)
title(‘Phase’)
ylabel(‘°’) In a partially unknown system, I measured a square-wave signal as input and the associated system response. Now I would like to use fft() to determine the transfer function or the Bode diagram. I have attached the measurements. I have the following code (also from this forum) but it results in this very bad bode plot. where is my mistake?
input = x3bzeit((23000:39000),2);
output = x3bzeit((23000:39000),3);
time = x3bzeit((23000:39000),1)*10^(-6);

Fs = 1/mean(diff(time)); % Sampling Frequency
Fn = Fs/2; % Nyquist Frequency
L = numel(time);
FTinp = fft(input)/L;
FTout = fft(output)/L;
TF = FTout ./ FTinp; % Transfer Function
Fv = linspace(0, 1, fix(L/2)+1)*Fn; % Frequency Vector
Iv = 1:numel(Fv); % Index Vector
figure
subplot(2,1,1)
plot(Fv, 20*log10(abs(TF(Iv))))
set(gca, ‘XScale’, ‘log’)

title(‘Amplitude’)
ylabel(‘dB’)
subplot(2,1,2)
plot(Fv, angle(TF(Iv))*180/pi)
title(‘Phase’)
ylabel(‘°’) bode, transfer function, fft MATLAB Answers — New Questions

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