# Plotting a magnitude response calculated by hand

조회 수: 19 (최근 30일)
Stine Bech Petersen 2018년 12월 5일
답변: Astha Singh 2018년 12월 12일
I have calculated a magnitude response and phase response by hand as:
| H(w) | = | 0.5*[1+cos(w)] |
<H(w) = -w
And now I want to plot the magnitude response, but it does not look like I would expect it to (a lowpass filter). The plot is shown below.
I'm pretty sure my equations are right. So how do it get it to actually look like a magnitude response in the plot?

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### 답변 (1개)

Astha Singh 2018년 12월 12일
Hello Stine,
To obtain the expected plot of the magnitude of the frequency response, you would need to plot the same in the frequency (here, 'w') range: (-π,π).
You can set the X-Tick labels in the plot accordingly.
A sample code is attached
w=-linspace(-pi , pi, 100);
mag = abs( 0.5*(1+cos(w)) );
plot(w,mag)
xticks(-pi: pi/2 : pi)
xticklabels({'-\pi', '-\pi/2','0','\pi/2','\pi'})
This leads to the expected low pass frequency response curve for the above system.

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