2FSK调制与解调的程序

1、fs=2000; %抽样频率dt=1/fs;f1=20; %定义两列载波的频率f2=100;a=round(rand(1,10); %产生二进制随机序列g1=a;g2=a;g11=(ones(1,2000)*g1; %产生方波信号g1a=g11(:); g21=(ones(1,2000)*g2;g2a=g21(:);t=0:dt:10-dt;t1=length(t);tuf1=cos(2*pi*f1.*t)tuf2=cos(2*pi*f2.*t)subplot(311)n=0:9;x=square(1,50);stem(0:9,a*x);grid;xlabel(二进制随机序列)ylabel(幅

2、度)subplot(312);plot(t,tuf1);title(频率为f1的余弦波)ylabel(幅度)subplot(313);plot(t,tuf2);title(频率为f2的余弦波)ylabel(幅度)figure(2)fsk1=g1a.*tuf1;fsk2=g2a.*tuf2;fsk=fsk1+fsk2;no=0.01*randn(1,t1);%噪声sn=fsk+no;subplot(211);plot(t,fsk);title(2fsk波形)ylabel(幅度)subplot(212);plot(t,sn);title(加入高斯噪声后的2fsk波形)ylabel(幅度的大小)xl

3、abel(t)figure(3) %FSK解调b1=fir1(101,10/800 20/800);b2=fir1(101,90/800 110/800); %设置带宽参数H1=filter(b1,1,sn); %b1为分子，1为分母，sn为滤波器输入序列H2=filter(b2,1,sn); %噪声信号同时通过两个滤波器subplot(211);plot(t,H1);title(经过带通滤波器H1后的波形) %画出经过H1滤波器后的波形ylabel(幅度);subplot(212);plot(t,H2); %画出经过滤波器二后的波形title(经过带通滤波器H2后的波形)ylabel(幅度)

4、xlabel(t)sw1=H1.*H1; %相干解调乘以同频同相的载波sw2=H2.*H2;%经过相乘器 figure(4)subplot(211);plot(t,sw1);title(经过相乘器h1后的波形) %画出乘以同频同相载波后的波形ylabel(幅度)subplot(212);plot(t,sw2);title(经过相乘器h2后的波形)ylabel(.幅度)xlabel(t)bn=fir1(101,2/800 10/800); %经过低通滤波器figure(5)st1=filter(bn,1,sw1);st2=filter(bn,1,sw2);subplot(211);plot(t,

5、st1);title(经过低通滤波器sw1后的波形) %经过低通滤波器，滤出频率ylabel(幅度) %为f1,f2的基带调制信号波形subplot(212);plot(t,st2);title(经过低通滤波器sw2后的波形)ylabel(幅度)xlabel(t)%判决for i=1:length(t) if(st1(i)=st2(i) st(i)=0; else st(i)=st2(i); end endfigure(6)st=st1+st2;subplot(211);plot(t,st);title(经过抽样判决器后的波形) %画出经过抽样判决的波形 ylabel(幅度)subplot(2

6、12);plot(t,sn);title(原始的波形)ylabel(幅度)xlabel(t)figure(7)y1=fftshift(a);%对调制信号进行傅里叶变换plot(abs(fft(y1); grid;title(调制信号的频谱图);axis(0,125,1,5);figure(8)y2=fftshift(tuf1);%对载波信号进行傅里叶变换plot(abs(fft(y2);grid;title(载波1的频谱图);axis(0,1000,0,0.);figure(9)y3=fftshift(tuf2);plot(abs(fft(y3);grid;title(载波2的频谱图);axis(500,1500,0,0.);fi