幅度調(diào)制AM信號(hào)輸出和功率譜程序清單

1、Ml調(diào)制信號(hào)及其包絡(luò)0051152253354456AM信號(hào)功率譜f%幅度調(diào)制AM信號(hào)輸出和功率譜程序清單dt=0.001;%時(shí)間采樣頻譜fmax=1;%信源最高頻譜fc=10;%載波中心頻率T=5;%信號(hào)時(shí)長(zhǎng)N=T/dt;t=0:N-1*dt;mt=sqrt(2)*cos(2*pi*fmax*t);%信源A=2;s_am=(A+mt).*cos(2*pi*fc*t);f,Xf=FFT_SHIFT(t,s_am);%調(diào)制信號(hào)頻譜PSD=(abs(Xf).A2)/T;%調(diào)制信號(hào)功率譜密度f(wàn)igure(1)subplot(211);plot(t,s_am);holdon;%畫(huà)出AM信號(hào)波形plot

2、(t,A+mt,'r-');%表示AM包絡(luò)title('AM調(diào)制信號(hào)及其包絡(luò),);xlabel('t');subplot(212);%畫(huà)出功率譜圖形plot(f,PSD);axis(-2*fc2*fc01.5*max(PSD);title('AM信號(hào)功率譜,);xlabel('f);csm調(diào)制信號(hào)及其包絡(luò)2LJL1II|IJ_00.511.522.633.5446比日信號(hào)功率借%抑制載波雙邊帶調(diào)制DSBdt=0.001;%時(shí)間采樣頻譜fmax=1;%信源最高頻譜fc=10;%載波中心頻率T=5;%信號(hào)時(shí)長(zhǎng)t=0:dt:T;mt=sqrt(

3、2)*cos(2*pi*fmax*t);%信源s_dsb=mt.*cos(2*pi*fc*t);f,sf=FFT_SHIFT(t,s_dsb);%調(diào)制信號(hào)頻譜PSD=(abs(sf).A2)/T;%調(diào)制信號(hào)功率譜密度f(wàn)igure(1)subplot(211)plot(t,s_dsb);holdon;%畫(huà)出DSB信號(hào)波形plot(t,mt,'r-');%標(biāo)示mt波形title('DSB調(diào)制信號(hào)及其包絡(luò),);xlabel('t');subplot(212)plot(f,PSD);axis(-2*fc2*fc0max(PSD);title('DSB信號(hào)

4、功率譜,);%單邊帶調(diào)制SSBdt=0.001;%時(shí)間采樣頻譜fmax=1;%信源最高頻譜fc=10;%載波中心頻率T=5;t=0:dt:T;mt=sqrt(2)*cos(2*pi*fmax*t);%信源s_ssb=real(hilbert(mt).*exp(j*2*pi*fc*t);f,sf=FFT_SHIFT(t,s_ssb);%單邊帶信號(hào)頻譜PSD=(abs(sf).A2)/T;%單便帶信號(hào)功率譜figure(1)subplot(211)plot(t,s_ssb);holdon;%畫(huà)出SSB信號(hào)波形plot(t,mt,'r-');%標(biāo)示mt的包絡(luò)title('SS

5、B調(diào)制信號(hào)');xlabel('t');subplot(212)plot(f,PSD);axis(-2*fc2*fc0max(PSD);title('SSB信號(hào)功率譜,);xlabel('f);%調(diào)用函數(shù)functionf,sf=FFT_SHIFT(t,st)%ThisfunctionisFFTtocalculateasignaltransfosrFourier%Input:t:samplingtime,st:signaldata.Timelengthmustgreaterthean2%output:f:samplingfrequency,sf:freq

6、uen%outputisthefrequencyandthesignalspectrumdt=t(2)-t(1);T=t(end);df=1/T;N=length(t);f=-N/2:N/2-1*df;sf=fft(st);sf=T/N*fftshift(sf);%I%顯示模擬調(diào)制的波形及其解調(diào)方法VSB,文件名：VSB.m%Signaldt=0.001;fmax=5;fc=20;T=5;N=T/dt;t=0:N-1*dt;mt=sqrt(2)*(cos(2*pi*fmax*t)+sin(2*pi*0.5*fmax*t);%VSBmodulations_vsb=mt.*cos(2*pi*fc*

7、t);B1=0.2*fmax;B2=1.2*fmax;f,sf=FFT_SHIFT(t,s_vsb);t,s_vsb=vsbmd(f,sf,B1,B2,fc);%PowerSpectrumDensityf,sf=FFT_SHIFT(t,s_vsb);PSD=(abs(sf).A2)/T;%PlotVSBandPSDfigure(1)subplot(211)plot(t,s_vsb);holdon;plot(t,mt,'r-');title('VSB調(diào)制信號(hào),);xlabel('t');subplot(212)plot(f,PSD);axis(-2*fc2

8、*fc0max(PSD);title('VSB信號(hào)功率譜,);xlabel('f);%functiont,st=vsbmd(f,sf,B1,B2,fc)%Thisfunctionisaresidualbandpassfilter%Inputsf:samplefrequency,sf:frequencyspectrumdata%B1:residualbandwidth,B2:highestfreqofthebasebandsignal%Outputst:sampletime,st:signaldatadf=f(2)-f(1);T=1/df;hf=zeros(1,length(f)

9、;bf1=floor(fc-B1)/df):floor(fc+B1)/df);bf2=floor(fc-B1)/df)+1:floor(fc+B2)/df);f1=bf1+floor(length(f)/2);f2=bf2+floor(length(f)/2);stepf=1/length(f1);hf(f1)=0:stepf:1-stepf;hf(f2)=1;f3=-bf1+floor(length(f)/2);f4=-bf2+floor(length(f)/2);hf(f3)=0:stepf:(1-stepf);hf(f4)=1;yf=hf.*sf;t,st=IFFT_SHIFT(f,yf);st=real(st);%