Wrong phase plot generated by angle()

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Zhaoyang Li
Zhaoyang Li on 8 Oct 2021
Answered: Paul on 8 Oct 2021
I was trying to plot the phase spectrum of using the angle function, however matlab gives me which is incorrect since the phase of this signal is , and ω is undefined at -1 and 1. The correct plot should be . I wonder if I did something wrong or if it's something intertal of the angle() function.

Answers (1)

Paul
Paul on 8 Oct 2021
The four-quadrant arctangent is needed to find the angle of a (non-zero) complex number:
syms w real
X(w) = 1/(1 + 1j*w)^2;
phase(w) = atan2(simplify(imag(X)),simplify(real(X)))
phase(w) = 
angle(X(1))
ans = 
phase(1)
ans = 

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