代码:
%% ------------------------------------------------------------------------%% Output Info about this m-filefprintf('\n***********************************************************\n');fprintf('Exameple 8.6 \n\n');time_stamp = datestr(now, 31);[wkd1, wkd2] = weekday(today, 'long');fprintf(' Now is %20s, and it is %9s \n', time_stamp, wkd2);%% ------------------------------------------------------------------------Wp = 0.2*pi; Ws = 0.3*pi; Rp = 1; As =16;Ripple = 10 ^ (-Rp/20); Attn = 10 ^ (-As/20);% Analog filter design:[b, a] = afd_chb1(Wp, Ws, Rp, As);% Calculation of second-order sections:[C, B, A] = sdir2cas(b, a)% Calculation of Frequency Response:[db, mag, pha, ww] = freqs_m(b, a, 0.5*pi);% Calculation of Impulse Response:[ha, x, t] = impulse(b, a);%% -------------------------------------------------%% Plot%% ------------------------------------------------- figure('NumberTitle', 'off', 'Name', 'Exameple 8.6')set(gcf,'Color','white'); M = 0.5; % Omega maxsubplot(2,2,1); plot(ww/pi, mag); axis([0, M, 0, 1.2]); grid on;xlabel(' Analog frequency in \pi units'); ylabel('|H|'); title('Magnitude Response');set(gca, 'XTickMode', 'manual', 'XTick', [0, 0.2, 0.3, M]);set(gca, 'YTickMode', 'manual', 'YTick', [0, 0.1585, 0.8913, 1]);subplot(2,2,2); plot(ww/pi, db); axis([0, M, -30, 10]); grid on;xlabel('Analog frequency in \pi units'); ylabel('Decibels'); title('Magnitude in dB ');set(gca, 'XTickMode', 'manual', 'XTick', [0, 0.2, 0.3, M]);set(gca, 'YTickMode', 'manual', 'YTick', [-30, -16, -1, 0]);subplot(2,2,3); plot(ww/pi, pha/pi); axis([0, M, -1.1, 1.1]); grid on;xlabel('Analog frequency in \pi nuits'); ylabel('radians in \pi units'); title('Phase Response');set(gca, 'XTickMode', 'manual', 'XTick', [0, 0.2, 0.3, M]);set(gca, 'YTickMode', 'manual', 'YTick', [-1:0.5:1]);subplot(2,2,4); plot(t, ha); axis([0, 50, -0.1, 0.25]); grid on;xlabel('time in seconds'); ylabel('ha(t)'); title('Impulse Response');
运行结果: