• 《DSP using MATLAB》Problem 5.15


    代码:

    %% ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
    %%            Output Info about this m-file
    fprintf('
    ***********************************************************
    ');
    fprintf('        <DSP using MATLAB> Problem 5.15 
    
    ');
    
    banner();
    %% ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
    
    % ------------------------------------------------------------------------
    %       1  x(n) = [1, -2, 3, 1,-2,3, 1, -2, 3, 1, -2, 3,1,-2,3,1,-2,3] 
    %                    N=18    N=2uv
    %                   x(n) = x(n+v)                                    
    % ------------------------------------------------------------------------
     
    nn1 = [0:17];
    xx1 = [1, -2, 3, 1, -2, 3, 1, -2, 3, 1, -2, 3, 1, -2, 3, 1, -2, 3];
    NN1 = length(xx1);                                % length is 18
    
    
    %m = mod_1(nn1, NN1);
    %x = [xx1 zeros(1, 0)];                        % padding zeros
    %n = [nn1 max(nn1)+1:max(nn1)+6];
    x = xx1;
    n = nn1;
    
    figure('NumberTitle', 'off', 'Name', 'P5.15.1 x(n)')
    set(gcf,'Color','white'); 
    subplot(2,1,1); stem(nn1, xx1);
    xlabel('n'); ylabel('x(n)');
    title('x(n) ori sequence');  grid on;
    subplot(2,1,2); stem(n, x);
    xlabel('n'); ylabel('x(n)');
    title('x(n) padding 0 zeros');  grid on;
    
    
    %% =============================================================================
    %%                 DTFT X(w) of xn sequence, w=[0:2pi], 
    %% =============================================================================
    MM = 500;
    [Xw_DTFT, w] = dtft1(x, n, MM);
    
     magXw_DTFT = abs(Xw_DTFT);   angXw_DTFT = angle(Xw_DTFT)/pi; 
    realXw_DTFT = real(Xw_DTFT); imagXw_DTFT = imag(Xw_DTFT);
    
    
    %% --------------------------------------------------------------
    %%        START X_DTFT's  mag ang real imag
    %% --------------------------------------------------------------
    figure('NumberTitle', 'off', 'Name', 'P5.15.1 X(w) DTFT of x(n)');
    set(gcf,'Color','white'); 
    subplot(2,2,1); plot(w/pi,magXw_DTFT); grid on;  % axis([-2,2,0,15]); 
    title('Magnitude Part');
    xlabel('frequency in pi units'); ylabel('Magnitude  |X\_DTFT|'); 
    subplot(2,2,3); plot(w/pi, angXw_DTFT); grid on;  % axis([-2,2,-1,1]);
    title('Angle Part');
    xlabel('frequency in pi units'); ylabel('Rad pi'); %axis([-200,200,0,2]);
    
    subplot('2,2,2'); plot(w/pi, realXw_DTFT); grid on;
    title('Real Part');
    xlabel('frequency in pi units'); ylabel('Real');
    subplot('2,2,4'); plot(w/pi, imagXw_DTFT); grid on;
    title('Imaginary Part');
    xlabel('frequency in pi units'); ylabel('Imaginary');
    %% --------------------------------------------------------------
    %%        END X_DTFT's  mag ang real imag
    %% --------------------------------------------------------------
    
    
    %% ------------------------------------------------------------------
    %%                 DFT(k) of xn sequence, k=[0:N-1]
    %%                      w=2pi*k/N       k=Nw/(2pi)
    %% ------------------------------------------------------------------
    N1 = length(x);
    k1 = [0 : N1-1];
    %k2 = [-N : N-1];
    %k3 = [-N/2 : N/2];
    Xk_DFT = dft(x, N1);                                         % DFT
        magXk_DFT = abs( [ Xk_DFT ] );                          % DFT magnitude
        angXk_DFT = angle( [Xk_DFT] )/pi;                       % DFT angle
       realXk_DFT = real(Xk_DFT); imagXk_DFT = imag(Xk_DFT);
    
    figure('NumberTitle', 'off', 'Name', 'P5.15.1 DFT(k) of x(n)')
    set(gcf,'Color','white'); 
    subplot(2,1,1); stem(k1, magXk_DFT); hold on; plot(N1*w/(2*pi), magXw_DTFT,'r--'); hold off;
    %axis([-N/2, N/2, -0.5, 50.5]);
    xlabel('k'); ylabel('magnitude(k)');
    title('DFT magnitude of x(n), N=18');  grid on;
    subplot(2,1,2); stem(k1, angXk_DFT);  hold on; plot(N1*w/(2*pi), angXw_DTFT,'r--'); hold off;
    %axis([-N/2, N/2, -0.5, 50.5]);
    xlabel('k'); ylabel('angle(k)');
    title('DFT angle of x(n), N=18'); grid on;
    

      运行结果:

             第2小题:

    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/9379485.html
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