Frequency response!!

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Foxbat
Foxbat 2011-4-13
Dear All,
I am a bit puzzled with obtaining the frequency response of my system! I am applying a voltage V(t) at a certain frequency f, and I have computed the resulting current as I(t). I want to get the frequency response from these two sine waves! lets say the real and imaginary part of the impedance.
Could you show me a simple procedure to get it!! should I use "system identification toolbox"? or are there any alternative ways!
Thanks in advance
  2 个评论
Jarrod Rivituso
Jarrod Rivituso 2011-4-13
What format is your system in? Is it a Simulink model? Or an LTI object? Or something else?
Foxbat
Foxbat 2011-4-13
Thanks, No, it is not a Simulink model! it is calculated from another software "Comsol" by using matlab (M-file). It is a physical system in which I am interested to get the frequency response. so as a result I have I(t) as output data and V(t) as input!

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采纳的回答

Rajiv Singh
Rajiv Singh 2011-4-13
Please see tfestimate (Signal Processing Toolbox), spa, spafdr, etfe (System Identification Toolbox) for functions that calculate the frequency response from time domain signals in a non-parametric (empirical) fashion.
Perhaps a more reliable way is to compute a dynamic linear model from the data and then obtain the frequency response by calling BODE or FREQRESP on it. For example:
z = iddata(I, V, Ts); % Ts is sample time
model = n4sid(z, 1:10); % state-space model or order between 1 and 10
H = freqresp(model, linspace(0, pi/Ts, 100)); % the frequency response
This requires System Identification Toolbox.

更多回答（1 个）

Arnaud Miege
Arnaud Miege 2011-4-13
If you have two time series, you probably need to use fft to convert the data into the time domain and compute the frequency response.
HTH,
Arnaud

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