代码：
第1小题：
%% ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
%% Output Info about this m-file
fprintf('\n***********************************************************\n');
fprintf(' <DSP using MATLAB> Problem 5.10 \n\n');
banner();
%% ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
% --------------------------------------------------------------
% 1 x(n) = 0.6^abs(n)[u(n+10)-u(n-11)]
% --------------------------------------------------------------
nn1 = [-15:16];
xx1 = 0.6 .^ abs(nn1) .* (stepseq(-10, min(nn1), max(nn1)) - stepseq(11, min(nn1), max(nn1)));
NN1 = length(xx1); % length is 32
m = mod_1(nn1, NN1);
x = [xx1 zeros(1, 8)]; % padding zeros
n = [m max(m)+1:max(m)+8];
figure('NumberTitle', 'off', 'Name', 'P5.10.1 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 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', 'P5.10.1 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', 'P5.10.1 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=40'); 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=40'); grid on;
运行结果：
第4小题：
%% ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
%% Output Info about this m-file
fprintf('\n***********************************************************\n');
fprintf(' <DSP using MATLAB> Problem 5.10 \n\n');
banner();
%% ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
% ------------------------------------------------------------------
% 4 x(n) = [1 2 3 4 3 2 1]
% |
% ------------------------------------------------------------------
nn1 = [-3:3];
xx1 = [1 2 3 4 3 2 1];
NN1 = length(xx1); % length is 7
m = mod_1(nn1, NN1);
x = [xx1 zeros(1, 9)]; % padding 9 zeros
n = [m max(m)+1:max(m)+9]; % length is 16
figure('NumberTitle', 'off', 'Name', 'P5.10.4 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 zeros'); grid on;
%% =============================================================================
%% DTFT X(w) of xn sequence, w=[0:2pi],
%% =============================================================================
MM = 500;
[Xw_DTFT, w] = dtft1(xx1, m, 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', 'P5.10.4 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', 'P5.10.4 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=16'); 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=16'); grid on;
运行结果：
这里只放两个序列的，至于DFT的长度N选择的方法，我也没搞懂，欢迎博友赐教！