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  • 《DSP using MATLAB》示例Example 8.24

    代码:

    %% ------------------------------------------------------------------------
    %%            Output Info about this m-file
    fprintf('
    ***********************************************************
    ');
    fprintf('        <DSP using MATLAB> Exameple 8.24 
    
    ');
    
    time_stamp = datestr(now, 31);
    [wkd1, wkd2] = weekday(today, 'long');
    fprintf('      Now is %20s, and it is %8s  
    
    ', time_stamp, wkd2);
    %% ------------------------------------------------------------------------
    
    % Digital Filter Specifications:
    wp = 0.2*pi;                 % digital passband freq in rad
    ws = 0.3*pi;                 % digital stopband freq in rad
    Rp = 1;                      % passband ripple in dB
    As = 15;                     % stopband attenuation in dB
    
    % Analog prototype specifications: Inverse Mapping for frequencies
    T = 1;                           % set T = 1
    OmegaP = (2/T)*tan(wp/2);        % Prewarp(Cutoff) prototype passband freq
    OmegaS = (2/T)*tan(ws/2);        % Prewarp(cutoff) prototype stopband freq
    
    % Analog Elliptic Prototype Order Calculations:
    ep = sqrt(10^(Rp/10)-1);           % Passband Ripple Factor
    A = 10^(As/20);                    % Stopband Attenuation Factor
    OmegaC = OmegaP;                   % Analog Elliptic prototype cutoff freq
    k = OmegaP/OmegaS;                 % Analog prototype Transition ratio
    k1 = ep/sqrt(A*A-1);               % Analog prototype Intermediate cal
    capk = ellipke([k.^2 1-k.^2]);
    capk1 = ellipke([(k1 .^2) 1-(k1 .^2)]);
    
    N  = ceil(capk(1)*capk1(2)/(capk(2)*capk1(1)));
    fprintf('
    
     ********** Elliptic Filter Order = %3.0f  
    ', N)
    
    % Digital Chebyshev-2 Filter Design:
    wn = wp/pi;                        % Digital cutoff freq in pi units
    
    [b, a] = ellip(N, Rp, As, wn); [C, B, A] = dir2cas(b, a)
    
    % Calculation of Frequency Response:
    [db, mag, pha, grd, ww] = freqz_m(b, a);
    
    
    %% -----------------------------------------------------------------
    %%                             Plot
    %% -----------------------------------------------------------------  
    
    figure('NumberTitle', 'off', 'Name', 'Exameple 8.24')
    set(gcf,'Color','white'); 
    M = 1;                          % Omega max
    
    subplot(2,2,1); plot(ww/pi, mag); axis([0, M, 0, 1.2]); grid on;
    xlabel(' frequency in pi units'); ylabel('|H|'); title('Magnitude Response');
    set(gca, 'XTickMode', 'manual', 'XTick', [0, 0.2, 0.3, M]);
    set(gca, 'YTickMode', 'manual', 'YTick', [0, 0.1778, 0.8913, 1]);
    
    subplot(2,2,2); plot(ww/pi, pha/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, 0.2, 0.3, M]);
    set(gca, 'YTickMode', 'manual', 'YTick', [-1:1:1]);
    
    subplot(2,2,3); plot(ww/pi, db); axis([0, M, -30, 10]); grid on;
    xlabel('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, -15, -1, 0]);
    
    
    subplot(2,2,4); plot(ww/pi, grd); axis([0, M, 0, 15]); grid on;
    xlabel('frequency in pi units'); ylabel('Samples'); title('Group Delay');
    set(gca, 'XTickMode', 'manual', 'XTick', [0, 0.2, 0.3, M]);
    set(gca, 'YTickMode', 'manual', 'YTick', [0:5:15]);
    

      运行结果:

    牢记: 1、如果你决定做某事,那就动手去做;不要受任何人、任何事的干扰。2、这个世界并不完美,但依然值得我们去为之奋斗。
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  • 原文地址:https://www.cnblogs.com/ky027wh-sx/p/6732820.html
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