Question

The phase margin (in degrees) of a system having the loop transfer function G(s)  H(s)=2√3/s(s+1) is:

(a) 45°

(b) -30°

(c) 60°

(d) 30°

This question was posed to me during an interview.

My doubt is from Assessment of Relative Stability Using Nyquist Criterion topic in section Stability in Frequency Domain of Control Systems

Answer 1

The correct choice is (d) 30°

For explanation I would say: Phase margin is calculated at gain cross over frequency where magnitude of the transfer function is 1.