2fsk信号调制解调频谱的matlab仿真

2FSK信号的调制解调与频谱绘制的matlab仿真 a=randint(1,16); t=0.0001:0.001:1; inisig=a(ceil(t./(1/15))); subplot(5,1,1) plot(t,inisig) axis([0,1,-1.5,1.5]) title( 原信号 ); %调制 f1=200; f2=100; carrier1=cos(2*pi*f1*t); carrier2=cos(2*pi*f2*t); modulation_wave=zeros(1,length(t)); for i=1:length(t) if(inisig(i)==0) modulation_wave(i)=carrier1(i); else modulation_wave(i)=carrier2(i); end end subplot(5,1,2) plot(t,modulation_wave) axis([0,1,-1.5,1.5]) title( 调制信号 ); %2fsk信号加噪 noise_wave=awgn(modulation_wave,100); %设计带通滤波器 [num1 den1]=butter(10,[2*0.9*f1*pi,2*1.1*f1*pi], s ); [num2 den2]=butter(10,[2*0.9*f2*pi,2*1.1*f2*pi], s ); daiout1_h=tf(num1,den1); daiout2_h=tf(num2,den2); unmodulation_wave1=lsim(daiout1_h,noise_wave,t); unmodulation_wave2=lsim(daiout2_h,noise_wave,t); %2fsk信号相干解调 unmodulation_wave1_g=unmodulation_wave1 .*(carrier1); unmodulation_wave2_g=unmodulation_wave2 .*(carrier2); %设计低通滤波器 wp=2*pi*90; ws=2*pi*120; rp=1; rs=100; [N Wn]=buttord(wp,ws,rp,rs, s ); [B A]=butter(N,Wn, s ); h=tf(B,A); dsy1=lsim(h,unmodulation_wave1_g,t); dsy2=lsim(h,unmodulation_wave2_g,t); subplot(5,1,3); plot(t,dsy1); title( 经过一路低通滤波器后的信号 ); subplot(5,1,4); plot(t,dsy2); title( 经过二路低通滤波器后的信号 ); for i=1:length(dsy1) if dsy1(i)>dsy2(i) dsy(i)=0; else dsy(i)=1; end end subplot(5,1,5); plot(t,dsy); axis([0 1.2 -1.2 1.2]) title( 解调信号 ); %观察原信号频谱 inisig_spectrum=fftshift(fft(inisig)); maxf=1/0.001; f=-maxf/2:maxf/2-1; figure subplot(5,1,1); plot(f,inisig_spectrum) title( 观察原信号频谱 ); %观察调制信号频谱 modulation_spectrum=fftshift(fft(modulation_wave)); maxf=1/0.001; f=-maxf/2:maxf/2-1; subplot(5,1,2); plot(f,modulation_spectrum) title( 观察调制信号频谱 ); %观察带通信号频谱 unmodulation1_spectrum=fftshift(fft(unmodulation_wave1)); maxf=1/0.001; f=-maxf/2:maxf/2-1; subplot(5,1,4); plot(f,unmodulation1_spectrum) title( 观察带通信号150频谱 ); unmodulation2_spectrum=fftshift(fft(unmodulation_wave2)); maxf=1/0.001; f=-maxf/2:maxf/2-1; subplot(5,1,3); plot(f,unmodulation2_spectrum) title( 观察带通信号100频谱 ); length(unmodulation_wave1) %观察低通滤波器频谱 dsy_spectrum=fftshift(fft(dsy)); maxf=1/0.001; f=-maxf/2:maxf/2-1; subplot(5,1,5); plot(f,dsy_spectrum) title( 观察低通信号100频谱 ); 信号频谱图 观察上图，调制解调的频谱搬移基本正确，调制到高频，又解调回到低频。 观察上图，解调出来的信号不完成正确。这主要是因为带通滤波器设计的不太好造成的。 From：qianmyi