How to use freqz to plot filter frequency response?

85 次查看（过去 30 天）
Christopher Saltonstall
评论： Kritika Gupta 2023-3-2
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')

请先登录，再回答此问题。

采纳的回答

Christopher Saltonstall
Its is because the frequency response, h, is a complex value. By plotting,
plot(f,h)
only the real (in-phase) component is plotted. Instead, the magnitude of h must be plotted,
plot(f,abs(h))

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 Digital Filter Analysis 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by