% Chapter 8: Example 8.28
%            Chebyshev-1 Highpass Filter Design:
%                Use of the CHEBY1 function
%
% Digital Filter Specifications:        % Type: Chebyshev-I highpass
ws = 0.4586*pi;                         % Dig. stopband edge frequency
wp = 0.6*pi;                            % Dig. passband edge frequency
Rp = 1;                                 % Passband ripple in dB
As = 15;                                % Stopband attenuation in dB
Ripple = 10 ^ (-Rp/20);                 % Passband ripple
Attn = 10 ^ (-As/20);                   % Passband attenuation

% Calculations of Chebyshev-I Filter Parameters:
[N,wn] = cheb1ord(wp/pi,ws/pi,Rp,As);

% Digital Chebyshev-I Highpass Filter Design:
[b,a] = cheby1(N,Rp,wn,'high');

% Cascade Form Realization:
[b0,B,A] = dir2cas(b,a)
%%b0 = 0.0243
%%B = 1.0000   -1.9991    0.9991
%%    1.0000   -2.0009    1.0009
%%A = 1.0000    1.0416    0.4019
%%    1.0000    0.5561    0.7647

% Plotting:
figure(1); subplot(1,1,1)
[db,mag,pha,grd,w] = freqz_m(b,a);
subplot(2,2,1);plot(w/pi,mag);grid;title('Magnitude Response')
xlabel('Digital frequency in pi units'); axis([0,1,0,1])
set(gca,'XTickMode','manual','XTick',[0;ws/pi;wp/pi;1])
set(gca,'XTickLabelMode','manual','XTickLabels',['  0 ';'0.46';'0.6 ';'  1 '])
set(gca,'YTickMode','manual','YTick',[0;Attn;Ripple;1])
subplot(2,2,3);plot(w/pi,db);grid;title('Magnitude in dB')
xlabel('frequency in pi units'); axis([0,1,-30, 0]);
ylabel('decibels')
set(gca,'XTickMode','manual','XTick',[0;ws/pi;wp/pi;1])
set(gca,'XTickLabelMode','manual','XTickLabels',['  0 ';'0.46';'0.6 ';'  1 '])
set(gca,'YTickMode','manual','YTick',[-30;-As;-Rp;0])
set(gca,'YTickLabelMode','manual','YTickLabels',['30';'15';' 1';' 0'])
subplot(2,2,2);plot(w/pi,pha/pi);grid;title('Phase Response')
xlabel('frequency in pi units');ylabel('phase in pi units'); axis([0,1,-1,1])
set(gca,'XTickMode','manual','XTick',[0;ws/pi;wp/pi;1])
set(gca,'XTickLabelMode','manual','XTickLabels',['  0 ';'0.46';'0.6 ';'  1 '])
subplot(2,2,4);plot(w/pi,grd);grid;title('Group Delay')
xlabel('frequency in pi units');
ylabel('delay in samples')
set(gca,'XTickMode','manual','XTick',[0;ws/pi;wp/pi;1])
set(gca,'XTickLabelMode','manual','XTickLabels',['  0 ';'0.46';'0.6 ';'  1 '])