function [b,a] = cheb1hpf(wp,ws,Rp,As)% IIR Highpass filter design using Chebyshev-1 prototype% [b,a] = cheb1hpf(wp,ws,Rp,As)%   b = Numerator polynomial of the highpass filter%   a = Denominator polynomial of the highpass filter%  wp = Passband frequency in radians%  ws = Stopband frequency in radians%  Rp = Passband ripple in dB%  As = Stopband attenuation in dB%% Determine the digital lowpass cutoff frequecies:wplp = 0.2*pi;alpha = -(cos((wplp+wp)/2))/(cos((wplp-wp)/2));wslp = angle(-(exp(-j*ws)+alpha)/(1+alpha*exp(-j*ws)));%% Compute Analog lowpass Prototype Specifications:T = 1; Fs = 1/T;OmegaP = (2/T)*tan(wplp/2);OmegaS = (2/T)*tan(wslp/2);% Design Analog Chebyshev Prototype Lowpass Filter:[cs,ds] = afd_chb1(OmegaP,OmegaS,Rp,As);% Perform Bilinear transformation to obtain digital lowpass[blp,alp] = bilinear(cs,ds,Fs);% Transform digital lowpass into highpass filterNz = -[alpha,1]; Dz = [1,alpha];[b,a] = zmapping(blp,alp,Nz,Dz);