GATE 2023 IN – Question 50
The phase margin of $G(s)=2(1-s)/(1+s)^2$ is ______ degrees (nearest integer).
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Correct answer: -2 to 2
Explanation
The magnitude is $|G(j\omega)|=2/\sqrt{1+\omega^2}$, so crossover occurs at $\omega=\sqrt3$. Phase is $-\tan^{-1}\omega-2\tan^{-1}\omega=-180^\circ$. Phase margin is $180^\circ-180^\circ=\boxed{0^\circ}$.