通信原理基于MATLAB的VSB实验及其波形图

1、基于matlab的vsb程序及其波形图一 运行程序(注意这5个程序要分开写成5份)% - % 显示模拟调制的波形及其解调方法vsb，文件名：vsb.m % signal dt=0.001; fmax=6; fc=45; t=5; n=t/dt; t=0:n-1*dt; mt=sqrt(2)*(cos(2*pi*fmax*t)+sin(2*pi*0.5*fmax*t); % vsb modulation s_vsb=mt.*cos(2*pi*fc*t); b1=0.2*fmax; b2=1.2*fmax; f,sf=fft_shift(t,s_vsb); t,s_vsb=vsbmd(f,sf,b

2、1,b2,fc); % power spectrum density f,sf=fft_shift(t,s_vsb); psd=(abs(sf).2)/t; % plot vsb and psd figure(1) subplot(211) plot(t,s_vsb);hold on; plot(t,mt,r-); title(vsb调制信号); xlabel(t); subplot(212) plot(f,psd); axis(-2*fc 2*fc 0 max(psd); title(vsb信号功率谱);xlabel(f);二 调用程序1% 调用函数 function f, sf=fft_s

3、hift(t, st) %this function is fft to calculate a signals fourier transform %input: t: sampling time , st : signal data. time length mustgreater thean 2 %output: f : sampling frequency , sf: frequen %output is the frequency and the signal spectrum dt=t(2)-t(1); t=t(end); df=1/t; n=length(t); f=-n/2:n

4、/2-1*df; sf=fft(st); sf=t/n*fftshift(sf);三 调用程序2function t,st=ifft_shift(f,sf) df=f(2)-f(1); fmax=(f(end)-f(1)+df); dt=1/fmax; n=length(f); t=0:n-1*dt; sf=fftshift(sf); st=fmax*ifft(sf); st=real(st)四 调用程序3function t,st=vsbmd(f,sf,b1,b2,fc) % this function is a residual bandpass filter % inputs f: sa

5、mple frequency, sf: frequency spectrum data % b1: residual bandwidth, b2: highest freq of the baseband signal % outputs t:sample time, st: signal data df=f(2)-f(1); t=1/df; hf=zeros(1,length(f); bf1=floor(fc-b1)/df):floor(fc+b1)/df); bf2=floor(fc-b1)/df)+1:floor(fc+b2)/df); f1=bf1+floor(length(f)/2); f2=bf2+floor(length(f)/2); stepf=1/length(f1); hf(f1)=0:stepf:1-stepf; hf(f2)=1; f3=-bf1+floor(length(f)/2); f4=-bf2+floor(length(f)/2);