Gain and Phase Margins: The closeness of the GH(jo)cure to-1 is a measure of the relative stability of the system. There are two numbers reflecting this measure Gain and Phase margin GM GM-gain margin ①三0 GM= GH(O) crossover freqency y-phase margin =PM=180°+∠GH(O,)GM=20lo 20logGHGo GHg180 ( ) u  = PM = +GH j