基于matlab的fsk的调制解调

%经典谱估计直接法实现FSK信号的解调 %中频fc为15MHz，采样率fs为50MHz %一个脉冲内5bit信息 %fs=n/tb，tb为码元宽度,n为一个码元内的采样点数 clear all; fs=5.0e+007; ts=1/fs; tb=5e-006;%码元宽度5us sample=tb/ts;%一个码元内采样250个点 fc=1.5e+007; f1=fc+8/(tb);%1.66e+007,对应1 f2=fc-8/(tb);%1.34e+007，对应0 B=5.0e+006; %对该输入信号FSK调制 Xin=[1,1,1,1,1,1,0,1,1,1];%randn(5,1)>0; tt=(0:tb/sample:tb-(tb/sample)); t=[tt;tt+tb;tt+2*tb;tt+3*tb;tt+4*tb;tt+5*tb;tt+6*tb;tt+7*tb;tt+8*tb;tt+9*tb]; y=zeros(10,length(tt)); for i=1:10 y(i,:)=Xin(i)*cos(2*pi*f1*t(i,:))+~Xin(i)*cos(2*pi*f2*t(i,:)); end t=reshape(t',length(tt)*10,1); y=reshape(y',length(tt)*10,1); %变换到基带 p1=cos(2*pi*fc*t-2*B*pi*t/2); z=y.*p1; %窗设计低通FIR滤波器 %假设信号带宽为3.5MHz fs=3.22e+007; fn=1.0e+007;%截止频率 Wn=fn/fs; N=127;%低通FIR滤波器的阶数 K=FIR1(N,Wn); H=zeros(1,2500); Y=conv(z,K); n=250; %截取后320个点 for j=1:2500 H(j)=Y(j+63); end %长度为1250 %解调FSK信号 %谱估计：直接法 k1=floor(250*(f1-fc+B/2)/fs) k2=floor(250*(f2-fc+B/2)/fs) for i=1:10 for j=1:n C(i,j)=H(j+(i-1)*n); end end OUT=zeros(1,10); for i=1:10 A=fft(C(i,:)); for j=1:n Pxx(j)=(abs(A(j))^2)/n; end if(Pxx(k1)>Pxx(k2)) OUT(i)=1; else OUT(i)=0; end end OUT