How to use freqz to plot filter frequency response?

Question

Christopher Saltonstall 2020-4-2

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/514720-how-to-use-freqz-to-plot-filter-frequency-response

评论： Kritika Gupta 2023-3-2

12x1_tranferFuncObj_v1.mat

I used systemIdentification to calculate the transfer function of my filter (see first figure) and then saved the idtf variable (attached). However, when I load the idtf variable and use freqz to plot the frequency response it looks very different (see second figure).

%number of frequencies
n = 50000;
%sampling frequency
f_sample = 2e8; %Hz
%transfer function numerator
b = [9.875702215802889e+04,6.459317537238607e+09];
%transfer function denominator
a = [1,1.844463395715939e+05,5.691593683410083e+09];
%calculate tranfer function response
[h_calc, w_calc] = freqz(b,a,n,f_sample);
%plot transfer function
figure(3)
plot(w_calc,h_calc)
set(gca,'XScale','log')
set(gca,'YScale','log')
xlabel('Frequency (Hz)')
ylabel('Filter Response')