2PSK数字信号的调制与解调

%Comparator

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % 判定并输出波形

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% High=2.5; Low=-2.5;

vt=0;%设立比较标准 error=0;

len1=length(so); for ii=1:len1 if so(ii) >= vt Vs(ii)=High; else

Vs(ii)=Low; end end Vo=Vs;

subplot(325);

plot (t,Vo), title('解调后输出信号'), axis([0 2e-4 -5 5]) grid on;

xlabel('时间 (s)'), ylabel('幅度(V)')

set (gcf, 'num', 'off', 'name', ['系统信号解调波形'... blanks(10)]);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % 系统调制信号频谱

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% T=t(end); df=1/T;

N=length(ask); f=(-N/2:N/2-1)*df; figure(3)

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % 信源频谱

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% xf=fftshift(abs(fft(x))); subplot(221) plot(f,xf)

title('信源频谱')

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % 调制信号频谱

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% askf=fftshift(abs(fft(ask))); subplot(222)

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plot(f,askf)

title('调制信号频谱')

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % 噪音信号频谱

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% noisef=fftshift(abs(fft(noise))); subplot(223) plot(f,noisef)

title('噪音信号频谱')

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % 调制后加噪音信号频谱

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% asknf=fftshift(abs(fft(askn))); subplot(224) plot(f,asknf)

title('调制后加噪音信号频谱')

set (gcf, 'num', 'off', 'name', ['系统调制信号频谱'... blanks(10)]);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % 通过带通滤波后信号频谱

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% figure(4)

fasknf=fftshift(abs(fft(faskn))); subplot(221) plot(f,fasknf)

title(' 通过带通滤波后信号频谱')

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % 通过相乘器后信号频谱

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% cmf=fftshift(abs(fft(cm))); subplot(222) plot(f,cmf)

title(' 通过相乘器后信号频谱') sof=fftshift(abs(fft(so))); subplot(223) plot(f,sof)

title('通过低通滤波器后输出信号频谱')

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % 通过判决解调后输出信号频谱

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Vof=fftshift(abs(fft(Vo))); subplot(224) plot(f,Vof)

title('通过判决解调后输出信号频谱')

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set (gcf, 'num', 'off', 'name', ['系统解调信号频谱'... blanks(10)]);

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