《DSP using MATLAB》示例Example 8.8

Posted 2020-09-09 沧海一粟

%% ------------------------------------------------------------------------
%%            Output Info about this m-file
fprintf(\'\\n***********************************************************\\n\');
fprintf(\'        <DSP using MATLAB> Exameple 8.8 \\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_elip(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 8.8\')
set(gcf,\'Color\',\'white\'); 
M = 0.5;                          % Omega max

subplot(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, 0.3]); grid on;
xlabel(\'time in seconds\'); ylabel(\'ha(t)\'); title(\'Impulse Response\');

　　运行结果：