《DSP using MATLAB》示例Example 8.30
%% ------------------------------------------------------------------------ %% Output Info about this m-file fprintf('\n***********************************************************\n'); fprintf(' <DSP using MATLAB> Exameple 8.30 \n\n'); time_stamp = datestr(now, 31); [wkd1, wkd2] = weekday(today, 'long'); fprintf(' Now is %20s, and it is %8s \n\n', time_stamp, wkd2); %% ------------------------------------------------------------------------ % Digital Filter Specifications: Chebyshev-2 bandpass ws = [0.4*pi 0.7*pi]; % digital stopband freq in rad wp = [0.25*pi 0.8*pi]; % digital passband freq in rad Rp = 1; % passband ripple in dB As = 40; % stopband attenuation in dB % Calculation of Chebyshev-2 filter parameters: [N, wn] = cheb2ord(wp/pi, ws/pi, Rp, As); fprintf('\n ********* Chebyshev-2 Filter Order is = %3.0f \n', N) % Digital Elliptic Bandpass Filter Design: [bhp, ahp] = cheby2(N, As, ws/pi, 'stop'); [C, B, A] = dir2cas(bhp, ahp) % Calculation of Frequency Response: %[dblp, maglp, phalp, grdlp, wwlp] = freqz_m(blp, alp); [dbhp, maghp, phahp, grdhp, wwhp] = freqz_m(bhp, ahp); %% ----------------------------------------------------------------- %% Plot %% ----------------------------------------------------------------- figure('NumberTitle', 'off', 'Name', 'Exameple 8.30') set(gcf,'Color','white'); M = 1; % Omega max subplot(2,2,1); plot(wwhp/pi, maghp); axis([0, M, 0, 1.2]); grid on; xlabel(' frequency in \pi units'); ylabel('|H|'); title('Magnitude Response'); set(gca, 'XTickMode', 'manual', 'XTick', [0, 0.25, 0.4, 0.7, 0.8, M]); set(gca, 'YTickMode', 'manual', 'YTick', [0, 0.8913, 1]); subplot(2,2,2); plot(wwhp/pi, dbhp); axis([0, M, -50, 2]); grid on; xlabel(' frequency in \pi units'); ylabel('Decibels'); title('Magnitude in dB'); set(gca, 'XTickMode', 'manual', 'XTick', [0, 0.25, 0.4, 0.7, 0.8, M]); set(gca, 'YTickMode', 'manual', 'YTick', [-50, -40, -1, 0]); subplot(2,2,3); plot(wwhp/pi, phahp/pi); axis([0, M, -1.1, 1.1]); grid on; xlabel('frequency in \pi nuits'); ylabel('radians in \pi units'); title('Phase Response'); set(gca, 'XTickMode', 'manual', 'XTick', [0, 0.25, 0.4, 0.7, 0.8, M]); set(gca, 'YTickMode', 'manual', 'YTick', [-1:0.5:1]); subplot(2,2,4); plot(wwhp/pi, grdhp); axis([0, M, 0, 15]); grid on; xlabel('frequency in \pi units'); ylabel('Samples'); title('Group Delay'); set(gca, 'XTickMode', 'manual', 'XTick', [0, 0.25, 0.4, 0.7, 0.8, M]); set(gca, 'YTickMode', 'manual', 'YTick', [0:5:15]);
运行结果:
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