2fsk信號調(diào)制解調(diào)頻譜的matlab仿真

1、2FSK言號的調(diào)制解調(diào)與頻譜繪制的 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(' 原信號 ');%調(diào)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) modulat

2、ion_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(' 調(diào)制信號 ');%2fsk 信號加噪noise_wave=awgn(modulation_wave,100);%設(shè)計帶通濾波器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

3、*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 信號相干解調(diào)unmodulation_wave1_g=unmodulation_wave1'.*(carrier1);unmodulation_wave2_g=unmodulation_wave2'.*(carrier2);%設(shè)計低通濾波器 wp=

4、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(' 經(jīng)過一路低通濾波器后的信號 '); subplot(5,1,4);plot(t,dsy2);title(' 經(jīng)過二路低通濾波器后的

5、信號 ');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(' 解調(diào)信號 '); %觀察原信號頻譜 inisig_spectrum=fftshift(fft(inisig);maxf=1/0.001;f=-maxf/2:maxf/2-1; figuresubplot(5,1,1); plot(f,inisig_spectrum) title(' 觀察原

6、信號頻譜 ');%觀察調(diào)制信號頻譜 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(' 觀察調(diào)制信號頻譜 ');%觀察帶通信號頻譜 unmodulation1_spectrum=fftshift(fft(unmodulation_wave1); maxf=1/0.001;f=-maxf/2:maxf/2-1; subplot(5,1,4);plot(f,un

7、modulation1_spectrum) title(' 觀察帶通信號 150 頻譜 ');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(' 觀察帶通信號 100 頻譜 '); length(unmodulation_wave1)%觀察低通濾波器頻譜 dsy_spectrum=fftshift(fft(dsy);maxf=1/

8、0.001; f=-maxf/2:maxf/2-1;subplot(5,1,5); plot(f,dsy_spectrum) title(' 觀察低通信號 100 頻譜 ');信號頻譜圖觀察原信號頻譜-500-400-300-200200300400500-100 0 100觀察帶通言號0頻普200-200-500-400-300-200-100100 200300400500觀察帶通信號5頻普觀察上圖，調(diào)制解調(diào)的頻譜搬移基本正確，調(diào)制到高頻，又解調(diào)回到低頻。原信號1 f0 - -100.10.20.30.40.50.60.70.80.91調(diào)制信號原信號00.10.20.30.40.50.60.70.80.91經(jīng)過一路低通濾波器后的信號1|T1II1IIf10 - - - /-1IIIIIIIII00.10.20.30.40.50.60.70.80.91經(jīng)過二路低通濾波器后的信號1|I1II1IITI0 -A =