% Figure 6.5
%
Omega = -pi:2*pi/300:pi;
X = 1./(1+0.5*exp(-j*Omega));
subplot(211),plot(Omega/pi,abs(X));
ylabel('|X(  )|');
subplot(212),plot(Omega/pi,180*angle(X)/pi);
ylabel(' X(  )')
subplot(111)
