%==========================================================================
%  Name：M_P.m
%  
%==========================================================================
clear;close all,
w=0:0.001:2*pi;
wc=0.25*pi;
H=u(w)-u(w-wc)+u(w-2*pi+wc)-u(w-2*pi);
subplot(221)
plot(w/pi,H,'k')
axis([0,1.98,-0.2,1.2])
xlabel('Frequency *pi')

grid on;title('The magnitde response H(ejw)');