function [Mol] = Nichols2(Gw, Mm)

   Gwp = unwrap(angle(Gw))*180/pi;
   Gwm = 20*log10(abs(Gw));

% M-Circle
   phase = [0:0.01:1]' * 2*pi;
   Mcl = Mm * exp(j*phase);
   Mol = Mcl ./ (1 - Mcl);
   Mp = unwrap(angle(Mol))*180/pi - 360;
   Mm = 20*log10(abs(Mol));
   plot(Gwp,Gwm,'b.-',Mp,Mm,'r');
   xlabel('Phase (degrees)');
   ylabel('Gain (dB)');
   xlim([-220,-120]);
   ylim([-30,20]);
   end