《2fsk信号调制解调频谱的matlab仿真.docxVIP

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);elsemodulation_wave(i)=carrier2(i); endendsubplot(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;endendsubplot(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;figuresubplot(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