E9.27 A unity feedback system has a loop transfer function (a) Determine the maximum gain K for which the phase margin is P.M. 30

E9.27 A unity feedback system has a loop transfer function

(a) Determine the maximum gain K for which the phase margin is P.M. Ú 30 and the gain margin is G.M. = 8 dB.

(b) Determine the value of gain K and cross over frequency for marginal stability.

L(s)G(s)G(s) = K s(5 + 3)