exa4_5.m

新版Matlab 7辅助信号处理技术与应用

% exa4-5_lp2hp for example4-5
% chebshev I analog lowpass filter prototype to highpass filter 

clear all;
N=9;
Rp=10;
wl=400*pi;
[z,p,k]=cheb1ap(N,Rp);
[b,a]=zp2tf(z,p,k);
% design analog highpass filter
[bt,at]=lp2hp(b,a,wl)
[H,w]=freqs(bt,at);
semilogy(w/pi,abs(H));
axis([0 3000 1e-8 1.1]);
xlabel('freq.(pi)');
ylabel('|H(jw)|');
grid on