Simulate a non linear system from input and output signals

My system is non linear. There is some harmonics in the output signal. Using this code i cant replicate my output signal. Simulated signal does not contain harmonics. How can i change the code?

clear all;close all;clc;

[inpSig,fs]=audioread('varFsin_1K.wav');

[outSig, Fs] = audioread('AliELENvarFsin_1K261104b500_8_23.wav');

windowLength = 256;

win = hamming(windowLength,"periodic");

overlap = round(0.75 * windowLength);

ffTLength = windowLength;

Ts=1;

data = iddata(outSig,inpSig,Ts)

nx = 10;

sys = ssest(data,nx);

compare(data,sys)

dt = 1/Fs;

t=0:dt:(length(inpSig)*dt)-dt;

z=lsim(sys,inpSig,t)

spectrogram(z,win,overlap,ffTLength,Fs,'yaxis');

Answer 1

[Ayush]

Hi @suniya vs

To replicate the harmonics in your output signal using the provided code, you can try the following steps:

• Increase the model complexity:

nx = 15; 
sys = ssest(data, nx); 

• Adjust the window length and overlap: Increasing the window length and reducing the overlap can provide a higher resolution spectrogram.

windowLength = 512;  % Increase the window length 
overlap = round(0.5 * windowLength);  % Reduce the overlap 

• Adjust the spectrogram parameters: Increasing ffTLength can provide a higher frequency resolution.

ffTLength = 1024;  % Increase the FFT length 

You may read further from here:

• https://in.mathworks.com/help/ident/ref/ssest.html
• https://in.mathworks.com/help/signal/ref/spectrogram.html

Thanks,

Ayush Jaiswal