% ----------------------------------------------------------------------------
% Example output from hpeq.m
%
% Designs with common 3-dB width
% ----------------------------------------------------------------------------
% Sophocles J. Orfanidis
% ECE Department, Rutgers University
% 94 Brett Road, Piscataway, NJ 08854-8058
%
% Email:   orfanidi@ece.rutgers.edu
% Date:    June 15, 2005
%
% Reference: Sophocles J. Orfanidis, "High-Order Digital Parametric Equalizer
%            Design," J. Audio Eng. Soc., vol.53, pp. 1026-1046, November 2005.
%
% Web Page: http://www.ece.rutgers.edu/~orfanidi/hpeq
%
% tested with MATLAB R11.1 and R14
% ----------------------------------------------------------------------------

clear all;

fs = 40;  f0 = 4;  Dfb = 2;  w0 = 2*pi*f0/fs; Dwb = 2*pi*Dfb/fs;

[wb1,wb2] = bandedge(w0,Dwb); fb1 = wb1*fs/2/pi; fb2 = wb2*fs/2/pi;

f = linspace(0,20,501); w = 2*pi*f/fs;

N = 4;

% ---------------------------- Butterworth --------------------------

type = 0;

G0 = 0; Gb=3; G = 12; GB = 9;

[B,A] = hpeq(N, G0, G, GB, w0, Dwb, type);

H = 20*log10(abs(fresp(B,A,w)));

figure;

plot(f,H,'b-');
hold on;

ylim([-8 14]); ytick(-6:3:12);
xlim([0,20]); xtick(0:2:20);
grid;

plot([fb1,f0,fb2], [GB,G,GB], 'k.', 'markersize',18);
hold off;

xlabel('{\it f}  (kHz)');
ylabel('dB');
title('{\it N} = 4, Butterworth');


% ---------------------------- Chebyshev-1 --------------------------

type = 1;

G0 = 0; G = 12; GB = 11.99; Gb = 9;

Dw = hpeqbw(N, G0, G, GB, Gb, Dwb, type);        % remap 3-dB width Dwb into the GB-width Dw

[w1,w2] = bandedge(w0,Dw); f1 = w1*fs/2/pi; f2 = w2*fs/2/pi;

[B,A] = hpeq(N, G0, G, GB, w0, Dw, type);

H = 20*log10(abs(fresp(B,A,w)));

figure;

plot(f,H,'b-');
hold on;

ylim([-8 14]); ytick(-6:3:12);
xlim([0,20]); xtick(0:2:20);
grid;

plot([fb1,f1,f0,f2,fb2], [Gb,GB,G,GB,Gb], 'k.', 'markersize',18);
hold off;

xlabel('{\it f}  (kHz)');
ylabel('dB');
title('{\it N} = 4, Chebyshev - 1');


% ---------------------------- Chebyshev-2 --------------------------

type = 2;

G0 = 0; G = 12; GB = 0.01;  Gb = 9;

Dw = hpeqbw(N, G0, G, GB, Gb, Dwb, type);            % remap 3-dB width Dwb into the GB-width Dw

[w1,w2] = bandedge(w0,Dw); f1 = w1*fs/2/pi; f2 = w2*fs/2/pi;

[B,A] = hpeq(N, G0, G, GB, w0, Dw, type);

H = 20*log10(abs(fresp(B,A,w)));

figure;

plot(f,H,'b-');
hold on;

ylim([-8 14]); ytick(-6:3:12);
xlim([0,20]); xtick(0:2:20);
grid;

plot([fb1,f1,f0,f2,fb2], [Gb,GB,G,GB,Gb], 'k.', 'markersize',18);
hold off;

xlabel('{\it f}  (kHz)');
ylabel('dB');
title('{\it N} = 4, Chebyshev - 2');


% ---------------------------- Elliptic --------------------------

type = 3;

G0 = 0; G = 12; GB = 11.99; Gs = 0.01;  Gb = 9;

Dw = hpeqbw(N, G0, G, GB, Gb, Dwb, type, Gs);        % remap 3-dB width Dwb into the GB-width Dw

[w1,w2] = bandedge(w0,Dw); f1 = w1*fs/2/pi; f2 = w2*fs/2/pi;

[B,A] = hpeq(N, G0, G, GB, w0, Dw, type, Gs);

e = ripple(G,GB,G0); es = ripple(G,Gs,G0);     % calculate stopband edge frequencies
k1 = e/es; k = ellipdeg(N,k1);
Ws = tan(Dw/2)/k; Dws = 2*atan(Ws);
[w1s,w2s] = bandedge(w0,Dws); f1s = fs * w1s/2/pi; f2s = fs * w2s/2/pi;

H = 20*log10(abs(fresp(B,A,w)));

figure;

plot(f,H,'b-');
hold on;

ylim([-8 14]); ytick(-6:3:12);
xlim([0,20]); xtick(0:2:20);
grid;

plot([f1s,fb1,f1,f0,f2,fb2,f2s], [Gs,Gb,GB,G,GB,Gb,Gs], 'k.', 'markersize',18);
hold off;

xlabel('{\it f}  (kHz)');
ylabel('dB');
title('{\it N} = 4, Elliptic');

Published with MATLAB® 7.0.4