bshape.m

本matlab函数实现基带信号的成形和眼图的观测

function y=bshape(x,fs,fb,N,alfa,delay);
%x为数字基带信号，fs为采样频率，fb为信息传输速率，N为升余弦滚降滤波器的阶数，alfa是滚降系数（0至1之间），delay是眼图的观测延时
%缺省值为：fs=16,fb=1,N=16,alfa=0.5,delay=8
if nargin<6; delay=8; end;
if nargin<5; alfa=0.5; end;
if nargin<4; N=16; end;
if nargin<3; fb=1; end;
if nargin<2; fs=16; end;
if nargin<1; x=pulse(randint(1,64)); end;
b=firrcos(N,fb,2*alfa*fb,fs);
y=filter(b,1,x); y=y/max(abs(y)); m=fs;
%.....................................................................
if nargin<1;
    dt=1/m; t=0:dt:(length(y)-1)*dt;
    subplot(2,1,1); plot(t,x,t,y);
    axis([10 50 -0.2 1.2]);
    set(gcf,'num','off','name', ...
        ['Baseband Shaping with a Raised Cosine Filter...(alfa=0.5), ' blanks(10) 'BBI 2000']);
    title('Pulse Signal'); h=get(gca,'children');
    set(h(1),'color','b'); set(h(2),'color',[0.9 0.8 0]);
    subplot(2,2,4);n=length(y); eyescat(y(m:n),fb,fs,delay);
    y=fft(y)/n; y=abs(y(1:fix(n/4)))*2;
    I=find(y<1e-04); y(I)=1e-04; y=20*log10(y);
    x=fft(x)/n; x=abs(x(1:fix(n/4)))*2;
    I=find(x<1e-04); x(I)=1e-04; x=20*log10(x);
    f1=m/n; f=0:f1:(length(y)-1)*f1;
    subplot(2,2,3);plot(f,x,f,y); h=get(gca,'children');
    set(h(1),'color','b'); set(h(2),'color',[.9 .8 0]);
    title('Power Spectrum'); xlabel('f/fb'); zoom xon;
end;