通信原理基于matlab的計(jì)算機(jī)仿真源代碼.doc

例 Error! No text of specified style in document.1%周期信號（方波）的展開,fb_jinshi.mclose all;clear all;N=100; %取展開式的項(xiàng)數(shù)為2N1項(xiàng) T=1;fs=1/T;N_sample=128; %為了畫出波形，設(shè)置每個(gè)周期的采樣點(diǎn)數(shù)dt = T/N_sample; t=0:dt:10*T-dt; n=-N:N;Fn = sinc(n/2).*exp(-j*n*pi/2);Fn(N+1)=0; ft = zeros(1,length(t);for m=-N:N ft = ft + Fn(m+N+1)*exp(j*2*pi*m*fs*t);end plot(t,ft)例 Error! No text of specified style in document.4利用FFT計(jì)算信號的頻譜并與信號的真實(shí)頻譜的抽樣比較。腳本文件T2F.m定義了函數(shù)T2F，計(jì)算信號的傅立葉變換。function f,sf= T2F(t,st)%This is a function using the FFT function to calculate a signals Fourier%Translation%Input is the time and the signal vectors,the length of time must greater%than 2%Output is the frequency and the signal spectrumdt = t(2)-t(1);T=t(end);df = 1/T;N = length(st); f=-N/2*df:df:N/2*df-df; sf = fft(st);sf = T/N*fftshift(sf);腳本文件F2T.m定義了函數(shù)F2T，計(jì)算信號的反傅立葉變換。function t st=F2T(f,sf)%This function calculate the time signal using ifft function for the input%signals spectrum df = f(2)-f(1);Fmx = ( f(end)-f(1) +df);dt = 1/Fmx;N = length(sf);T = dt*N; %t=-T/2:dt:T/2-dt;t = 0:dt:T-dt; sff = fftshift(sf);st = Fmx*ifft(sff); 另寫腳本文件fb_spec.m如下：%方波的傅氏變換, fb_spec.mclear all;close all;T=1;N_sample = 128;dt=T/N_sample; t=0:dt:T-dt;st=ones(1,N_sample/2), -ones(1,N_sample/2); %方波一個(gè)周期 subplot(211);plot(t,st);axis(0 1 -2 2);xlabel(t); ylabel(s(t);subplot(212);f sf=T2F(t,st); %方波頻譜plot(f,abs(sf); hold on;axis(-10 10 0 1);xlabel(f);ylabel(|S(f)|); %根據(jù)傅氏變換計(jì)算得到的信號頻譜相應(yīng)位置的抽樣值sff= T2*j*pi*f*0.5.*exp(-j*2*pi*f*T).*sinc(f*T*0.5).*sinc(f*T*0.5);plot(f,abs(sff),r-)例 Error! No text of specified style in document.5%信號的能量計(jì)算或功率計(jì)算,sig_pow.mclear all;close all;dt = 0.01;t = 0:dt:5; s1 = exp(-5*t).*cos(20*pi*t);s2 = cos(20*pi*t);E1 = sum(s1.*s1)*dt; %s1(t)的信號能量P2 = sum(s2.*s2)*dt/(length(t)*dt); %s2(t)的信號功率sf1 s1f= T2F(t,s1);f2 s2f= T2F(t,s2); df = f1(2)-f1(1);E1_f = sum(abs(s1f).2)*df; %s1(t)的能量,用頻域方式計(jì)算df = f2(2)-f2(1);T = t(end);P2_f = sum(abs(s2f).2)*df/T; %s2(t)的功率，用頻域方式計(jì)算figure(1)subplot(211)plot(t,s1);xlabel(t); ylabel(s1(t); subplot(212)plot(t,s2)xlabel(t); ylabel(s2(t); 例 Error! No text of specified style in document.6%方波的傅氏變換，sig_band.mclear all;close all;T=1;N_sample = 128;dt=1/N_sample; t=0:dt:T-dt;st=ones(1,N_sample/2) -ones(1,N_sample/2); df=0.1/T;Fx = 1/dt;f=-Fx:df:Fx-df;%根據(jù)傅氏變換計(jì)算得到的信號頻譜sff= T2*j*pi*f*0.5.*exp(-j*2*pi*f*T).*sinc(f*T*0.5).*sinc(f*T*0.5);plot(f,abs(sff),r-)axis(-10 10 0 1);hold on;sf_max = max(abs(sff);line(f(1) f(end),sf_max sf_max);line(f(1) f(end),sf_max/sqrt(2) sf_max/sqrt(2); %交點(diǎn)處為信號功率下降3dB處Bw_eq = sum(abs(sff).2)*df/T/sf_max.2; %信號的等效帶寬例 Error! No text of specified style in document.7%帶通信號經(jīng)過帶通系統(tǒng)的等效基帶表示，sig_bandpass.mclear all;close all;dt = 0.01;t = 0:dt:5; s1 = exp(-t).*cos(20*pi*t); %輸入信號f1 s1f= T2F(t,s1); %輸入信號的頻譜s1_lowpass = hilbert(s1).*exp(-j*2*pi*10*t); %輸入信號的等效基帶信號f2 s2f=T2F(t,s1_lowpass); %輸入等效基帶信號的頻譜 h2f = zeros(1,length(s2f);a b=find( abs(s1f)=max(abs(s1f) ); %找到帶通信號的中心頻率h2f( 201-25:201+25 )= 1;h2f( 301-25:301+25) = 1;h2f = h2f.*exp(-j*2*pi*f2); %加入線性相位， t1 h1 = F2T(f2,h2f); %帶通系統(tǒng)的沖激響應(yīng)h1_lowpass = hilbert(h1).*exp(-j*2*pi*10*t1); %等效基帶系統(tǒng)的沖激響應(yīng) figure(1)subplot(521);plot(t,s1);xlabel(t); ylabel(s1(t); title(帶通信號);subplot(523);plot(f1,abs(s1f);xlabel(f); ylabel(|S1(f)|); title(帶通信號幅度譜);subplot(522)plot(t,real(s1_lowpass);xlabel(t);ylabel(Res_l(t);title(等效基帶信號的實(shí)部);subplot(524)plot(f2,abs(s2f);xlabel(f);ylabel(|S_l(f)|);title(等效基帶信號的幅度譜);%畫帶通系統(tǒng)及其等效基帶的圖subplot(525)plot(f2,abs(h2f);xlabel(f);ylabel(|H(f)|);title(帶通系統(tǒng)的傳輸響應(yīng)幅度譜);subplot(527)plot(t1,h1);xlabel(t);ylabel(h(t);title(帶通系統(tǒng)的沖激響應(yīng)); subplot(526)f3 hlf=T2F(t1,h1_lowpass);plot(f3,abs(hlf);xlabel(f);ylabel(|H_l(f)|);title(帶通系統(tǒng)的等效基帶幅度譜); subplot(528)plot(t1,h1_lowpass);xlabel(t);ylabel(h_l(t);title(帶通系統(tǒng)的等效基帶沖激響應(yīng)); %畫出帶通信號經(jīng)過帶通系統(tǒng)的響應(yīng) 及 等效基帶信號經(jīng)過等效基帶系統(tǒng)的響應(yīng)tt = 0:dt:t1(end)+t(end);yt = conv(s1,h1); subplot(529)plot(tt,yt);xlabel(t);ylabel(y(t);title(帶通信號與帶通系統(tǒng)響應(yīng)的卷積) ytl = conv(s1_lowpass,h1_lowpass).*exp(j*2*pi*10*tt);subplot(5,2,10)plot(tt,real(yt);xlabel(t);ylabel(y_l(t)cos(20*pi*t);title(等效基帶與等效基帶系統(tǒng)響應(yīng)的卷積中心頻率載波)例 36%例：窄帶高斯過程，文件 zdpw.mclear all; close all;N0=1; %雙邊功率譜密度fc=10; %中心頻率B=1; %帶寬 dt=0.01;T=100;t=0:dt:T-dt;%產(chǎn)生功率為N0*B的高斯白噪聲P = N0*B;st = sqrt(P)*randn(1,length(t);%將上述白噪聲經(jīng)過窄帶帶通系統(tǒng)，f,sf = T2F(t,st); %高斯信號頻譜figure(1)plot(f,abs(sf); %高斯信號的幅頻特性 tt gt=bpf(f,sf,fc-B/2,fc+B/2); %高斯信號經(jīng)過帶通系統(tǒng) glt = hilbert(real(gt); %窄帶信號的解析信號，調(diào)用hilbert函數(shù)得到解析信號glt = glt.*exp(-j*2*pi*fc*tt); ff,glf=T2F( tt, glt );figure(2)plot(ff,abs(glf);xlabel(頻率(Hz); ylabel(窄帶高斯過程樣本的幅頻特性) figure(3)subplot(411);plot(tt,real(gt);title(窄帶高斯過程樣本)subplot(412)plot(tt,real(glt).*cos(2*pi*fc*tt)-imag(glt).*sin(2*pi*fc*tt)title(由等效基帶重構(gòu)的窄帶高斯過程樣本)subplot(413)plot(tt,real(glt);title(窄帶高斯過程樣本的同相分量)subplot(414)plot(tt,imag(glt);xlabel(時(shí)間t(秒); title(窄帶高斯過程樣本的正交分量) %求窄帶高斯信號功率;注：由于樣本的功率近似等于隨機(jī)過程的功率，因此可能出現(xiàn)一些偏差P_gt=sum(real(gt).2)/T;P_glt_real = sum(real(glt).2)/T;P_glt_imag = sum(imag(glt).2)/T; %驗(yàn)證窄帶高斯過程的同相分量、正交分量的正交性a = real(glt)*(imag(glt)/T;用到的子函數(shù)function t,st=bpf(f,sf,B1,B2)%This function filter an input at frequency domain by an ideal bandpass filter%Inputs:% f: frequency samples% sf: input data spectrum samples% B1: bandpasss lower frequency% B2: bandpasss higher frequency %Outputs:% t: frequency samples% st: output datas time samplesdf = f(2)-f(1);T = 1/df;hf = zeros(1,length(f); bf = floor( B1/df ): floor( B2/df ) ;bf1 = floor( length(f)/2 ) + bf;bf2 = floor( length(f)/2 ) - bf;hf(bf1)=1/sqrt(2*(B2-B1);hf(bf2)=1/sqrt(2*(B2-B1); yf=hf.*sf.*exp(-j*2*pi*f*0.1*T);t,st=F2T(f,yf);例 41%顯示模擬調(diào)制的波形及解調(diào)方法DSB，文件mdsb.m%信源close all;clear all;dt = 0.001; %時(shí)間采樣間隔 fm=1; %信源最高頻率fc=10; %載波中心頻率T=5; %信號時(shí)長t = 0:dt:T; mt = sqrt(2)*cos(2*pi*fm*t); %信源%N0 = 0.01; %白噪單邊功率譜密度%DSB modulations_dsb = mt.*cos(2*pi*fc*t);B=2*fm;%noise = noise_nb(fc,B,N0,t);%s_dsb=s_dsb+noise;figure(1)subplot(311)plot(t,s_dsb);hold on; %畫出DSB信號波形plot(t,mt,r-); %標(biāo)示mt的波形title(DSB調(diào)制信號);xlabel(t);%DSB demodulationrt = s_dsb.*cos(2*pi*fc*t);rt = rt-mean(rt);f,rf = T2F(t,rt);t,rt = lpf(f,rf,2*fm);subplot(312)plot(t,rt); hold on;plot(t,mt/2,r-);title(相干解調(diào)后的信號波形與輸入信號的比較);xlabel(t)subplot(313)f,sf=T2F(t,s_dsb);psf = (abs(sf).2)/T;plot(f,psf);axis(-2*fc 2*fc 0 max(psf);title(DSB信號功率譜);xlabel(f);function t st=lpf(f,sf,B)%This function filter an input data using a lowpass filter%Inputs: f: frequency samples% sf: input data spectrum samples% B: lowpasss bandwidth with a rectangle lowpass%Outputs: t: time samples% st: output datas time samplesdf = f(2)-f(1);T = 1/df;hf = zeros(1,length(f);bf = -floor( B/df ): floor( B/df ) + floor( length(f)/2 );hf(bf)=1;yf=hf.*sf;t,st=F2T(f,yf);st = real(st);例 42%顯示模擬調(diào)制的波形及解調(diào)方法AM,文件mam.m%信源close all;clear all;dt = 0.001; %時(shí)間采樣間隔 fm=1; %信源最高頻率fc=10; %載波中心頻率T=5; %信號時(shí)長t = 0:dt:T; mt = sqrt(2)*cos(2*pi*fm*t); %信源%N0 = 0.01; %白噪單邊功率譜密度 %AM modulationA=2;s_am = (A+mt).*cos(2*pi*fc*t);B = 2*fm; %帶通濾波器帶寬%noise = noise_nb(fc,B,N0,t); %窄帶高斯噪聲產(chǎn)生%s_am = s_am + noise; figure(1)subplot(311)plot(t,s_am);hold on; %畫出AM信號波形plot(t,A+mt,r-); %標(biāo)示AM的包絡(luò)title(AM調(diào)制信號及其包絡(luò));xlabel(t);%AM demodulationrt = s_am.*cos(2*pi*fc*t); %相干解調(diào)rt = rt-mean(rt);f,rf = T2F(t,rt);t,rt = lpf(f,rf,2*fm); %低通濾波subplot(312)plot(t,rt); hold on;plot(t,mt/2,r-);title(相干解調(diào)后的信號波形與輸入信號的比較);xlabel(t)subplot(313)f,sf=T2F(t,s_am);psf = (abs(sf).2)/T;plot(f,psf);axis(-2*fc 2*fc 0 max(psf);title(AM信號功率譜);xlabel(f);例 43%顯示模擬調(diào)制的波形及解調(diào)方法SSB，文件mssb.m%信源close all;clear all;dt = 0.001; %時(shí)間采樣間隔 fm=1; %信源最高頻率fc=10; %載波中心頻率T=5; %信號時(shí)長t = 0:dt:T; mt = sqrt(2)*cos(2*pi*fm*t); %信源%N0 = 0.01; %白噪單邊功率譜密度 %SSB modulations_ssb = real( hilbert(mt).*exp(j*2*pi*fc*t) );B=fm;%noise = noise_nb(fc,B,N0,t);%s_ssb=s_ssb+noise;figure(1)subplot(311)plot(t,s_ssb);hold on; %畫出SSB信號波形plot(t,mt,r-); %標(biāo)示mt的波形title(SSB調(diào)制信號);xlabel(t); %SSB demodulationrt = s_ssb.*cos(2*pi*fc*t);rt = rt-mean(rt);f,rf = T2F(t,rt);t,rt = lpf(f,rf,2*fm); subplot(312)plot(t,rt); hold on;plot(t,mt/2,r-);title(相干解調(diào)后的信號波形與輸入信號的比較);xlabel(t)subplot(313)f,sf=T2F(t,s_ssb);psf = (abs(sf).2)/T;plot(f,psf);axis(-2*fc 2*fc 0 max(psf);title(SSB信號功率譜);xlabel(f);例 44%顯示模擬調(diào)制的波形及解調(diào)方法VSB，文件mvsb.m%信源close all;clear all;dt = 0.001; %時(shí)間采樣間隔 fm=5; %信源最高頻率fc=20; %載波中心頻率T=5; %信號時(shí)長t = 0:dt:T; mt = sqrt(2)*( cos(2*pi*fm*t)+sin(2*pi*0.5*fm*t) ); %信源%VSB modulations_vsb = mt.*cos(2*pi*fc*t);B=1.2*fm;f,sf = T2F(t,s_vsb);t,s_vsb = vsbpf(f,sf,0.2*fm,1.2*fm,fc);figure(1)subplot(311)plot(t,s_vsb);hold on; %畫出VSB信號波形plot(t,mt,r-); %標(biāo)示mt的波形title(VSB調(diào)制信號);xlabel(t);%VSB demodulationrt = s_vsb.*cos(2*pi*fc*t); f,rf = T2F(t,rt);t,rt = lpf(f,rf,2*fm);subplot(312)plot(t,rt); hold on;plot(t,mt/2,r-);title(相干解調(diào)后的信號波形與輸入信號的比較);xlabel(t)subplot(313)f,sf=T2F(t,s_vsb);psf = (abs(sf).2)/T;plot(f,psf);axis(-2*fc 2*fc 0 max(psf);title(VSB信號功率譜);xlabel(f);function t,st=vsbpf(f,sf,B1,B2,fc)%This function filter an input by an residual bandpass filter%Inputs: f: frequency samples% sf: input data spectrum samples% B1: residual bandwidth% B2: highest freq of the basedband signal %Outputs: t: frequency samples% st: output datas time samplesdf = f(2)-f(1);T = 1/df;hf = zeros(1,length(f);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=F2T(f,yf);st = real(st);例 45%顯示模擬調(diào)制的波形及解調(diào)方法AM、DSB、SSB, %信源close all;clear all;dt = 0.001;fm=1;fc=10;t = 0:dt:5;mt = sqrt(2)*cos(2*pi*fm*t);N0 = 0.1; %AM modulationA=2;s_am = (A+mt).*cos(2*pi*fc*t);B = 2*fm;noise = noise_nb(fc,B,N0,t);s_am = s_am + noise; figure(1)subplot(321)plot(t,s_am);hold on;plot(t,A+mt,r-);%AM demodulationrt = s_am.*cos(2*pi*fc*t);rt = rt-mean(rt);f,rf = T2F(t,rt);t,rt = lpf(f,rf,2*fm);title(AM信號);xlabel(t);subplot(322)plot(t,rt); hold on;plot(t,mt/2,r-);title(AM解調(diào)信號);xlabel(t); %DSB modulations_dsb = mt.*cos(2*pi*fc*t);B=2*fm;noise = noise_nb(fc,B,N0,t);s_dsb=s_dsb+noise; subplot(323)plot(t,s_dsb);hold on;plot(t,mt,r-);title(DSB信號);xlabel(t);%DSB demodulationrt = s_dsb.*cos(2*pi*fc*t);rt = rt-mean(rt);f,rf = T2F(t,rt);t,rt = lpf(f,rf,2*fm);subplot(324)plot(t,rt); hold on;plot(t,mt/2,r-);title(DSB解調(diào)信號);xlabel(t);%SSB modulations_ssb = real( hilbert(mt).*exp(j*2*pi*fc*t) );B=fm;noise = noise_nb(fc,B,N0,t);s_ssb=s_ssb+noise;subplot(325)plot(t,s_ssb);title(SSB信號);xlabel(t);%SSB demodulationrt = s_ssb.*cos(2*pi*fc*t);rt = rt-mean(rt);f,rf = T2F(t,rt);t,rt = lpf(f,rf,2*fm);subplot(326)plot(t,rt); hold on;plot(t,mt/2,r-);title(SSB解調(diào)信號);xlabel(t);function out = noise_nb(fc,B,N0,t)%output the narrow band gaussian noise sample with single-sided power spectrum N0%at carrier frequency equals fc and bandwidth euqals Bdt = t(2)-t(1);Fmx = 1/dt; n_len = length(t);p = N0*Fmx;rn = sqrt(p)*randn(1,n_len);f,rf = T2F(t,rn); t,out = bpf(f,rf,fc-B/2,fc+B/2);例 46%FM modulation and demodulation，mfm.mclear all;close all; Kf = 5;fc = 10;T=5;dt=0.001;t = 0:dt:T; %信源fm= 1;%mt = cos(2*pi*fm*t) + 1.5*sin(2*pi*0.3*fm*t); %信源信號mt = cos(2*pi*fm*t); %信源信號%FM 調(diào)制A = sqrt(2);%mti = 1/2/pi/fm*sin(2*pi*fm*t) -3/4/pi/0.3/fm*cos(2*pi*0.3*fm*t); %mt的積分函數(shù)mti = 1/2/pi/fm*sin(2*pi*fm*t) ; %mt的積分函數(shù)st = A*cos(2*pi*fc*t + 2*pi*Kf*mti);figure(1)subplot(311);plot(t,st); hold on;plot(t,mt,r-);xlabel(t);ylabel(調(diào)頻信號) subplot(312)f sf = T2F(t,st);plot(f, abs(sf);axis(-25 25 0 3)xlabel(f);ylabel(調(diào)頻信號幅度譜) %FM 解調(diào)for k=1:length(st)-1 rt(k) = (st(k+1)-st(k)/dt;endrt(length(st)=0;subplot(313)plot(t,rt); hold on;plot(t,A*2*pi*Kf*mt+A*2*pi*fc,r-);xlabel(t);ylabel(調(diào)頻信號微分后包絡(luò))例 51%數(shù)字基帶信號的功率譜密度 digit_baseband.mclear all; close all;Ts=1;N_sample = 8; %每個(gè)碼元的抽樣點(diǎn)數(shù)dt = Ts/N_sample; %抽樣時(shí)間間隔N = 1000; %碼元數(shù)t = 0:dt:(N*N_sample-1)*dt; gt1 = ones(1,N_sample); %NRZ非歸零波形gt2 = ones(1,N_sample/2); %RZ歸零波形gt2 = gt2 zeros(1,N_sample/2);mt3 = sinc(t-5)/Ts); % sin(pi*t/Ts)/(pi*t/Ts)波形，截段取10個(gè)碼元gt3 = mt3(1:10*N_sample);d = ( sign( randn(1,N) ) +1 )/2;data = sigexpand(d,N_sample); %對序列間隔插入N_sample-1個(gè)0st1 = conv(data,gt1); %Matlab自帶卷積函數(shù)st2 = conv(data,gt2);d = 2*d-1; %變成雙極性序列data= sigexpand(d,N_sample); st3 = conv(data,gt3); f,st1f = T2F(t,st1(1:length(t);f,st2f = T2F(t,st2(1:length(t);f,st3f = T2F(t,st3(1:length(t); figure(1)subplot(321)plot(t,st1(1:length(t) );gridaxis(0 20 -1.5 1.5);ylabel(單極性NRZ波形);subplot(322);plot(f,10*log10(abs(st1f).2/T) );gridaxis(-5 5 -40 10); ylabel(單極性NRZ功率譜密度(dB/Hz); subplot(323)plot(t,st2(1:length(t) );axis(0 20 -1.5 1.5);gridylabel(單極性RZ波形);subplot(324)plot(f,10*log10(abs(st2f).2/T);axis(-5 5 -40 10);gridylabel(單極性RZ功率譜密度(dB/Hz); subplot(325)plot(t-5,st3(1:length(t) );axis(0 20 -2 2);gridylabel(雙極性sinc波形);xlabel(t/Ts);subplot(326)plot(f,10*log10(abs(st3f).2/T);axis(-5 5 -40 10);gridylabel(sinc波形功率譜密度(dB/Hz);xlabel(f*Ts); function out=sigexpand(d,M)%將輸入的序列擴(kuò)展成間隔為N-1個(gè)0的序列N = length(d);out = zeros(M,N);out(1,:) = d;out = reshape(out,1,M*N);例 52%數(shù)字基帶信號接收示意 digit_receive.mclear all;close all; N =100;N_sample=8; %每碼元抽樣點(diǎn)數(shù)Ts=1;dt = Ts/N_sample;t=0:dt:(N*N_sample-1)*dt; gt = ones(1,N_sample); %數(shù)字基帶波形d = sign(randn(1,N); %輸入數(shù)字序列a = sigexpand(d,N_sample); st = conv(a,gt); %數(shù)字基帶信號 ht1 = gt;rt1 = conv(st,ht1); ht2 = 5*sinc(5*(t-5)/Ts);rt2 = conv(st,ht2); figure(1)subplot(321)plot( t,st(1:length(t) );axis(0 20 -1.5 1.5); ylabel(輸入雙極性NRZ數(shù)字基帶波形);subplot(322)stem( t,a);axis(0 20 -1.5 1.5); ylabel(輸入數(shù)字序列) subplot(323)plot( t,0 rt1(1:length(t)-1)/8 );axis(0 20 -1.5 1.5);ylabel(方波濾波后輸出);subplot(324)dd = rt1(N_sample:N_sample:end);ddd= sigexpand(dd,N_sample);stem( t,ddd(1:length(t)/8 );axis(0 20 -1.5 1.5);ylabel(方波濾波后抽樣輸出); subplot(325)plot(t-5, 0 rt2(1:length(t)-1)/8 );axis(0 20 -1.5 1.5);xlabel(t/Ts); ylabel(理想低通濾波后輸出);subplot(326)dd = rt2(N_sample-1:N_sample:end);ddd=sigexpand(dd,N_sample);stem( t-5,ddd(1:length(t)/8 );axis(0 20 -1.5 1.5); xlabel(t/Ts); ylabel(理想低通濾波后抽樣輸出);例 57%部分響應(yīng)信號眼圖示意,pres.mclear all; close all;Ts=1;N_sample=16;eye_num = 11; N_data=1000; dt = Ts/N_sample;t = -5*Ts:dt:5*Ts; %產(chǎn)生雙極性數(shù)字信號d = sign(randn(1,N_data);dd= sigexpand(d,N_sample);%部分響應(yīng)系統(tǒng)沖擊響應(yīng)ht = sinc(t+eps)/Ts)./(1- (t+eps)./Ts);ht( 6*N_sample+1 ) = 1;st = conv(dd,ht);tt = -5*Ts:dt:(N_data+5)*N_sample*dt-dt; figure(1)subplot(211);plot(tt,st);axis(0 20 -3 3);xlabel(t/Ts);ylabel(部分響應(yīng)基帶信號);subplot(212)%畫眼圖ss=zeros(1,eye_num*N_sample);ttt = 0:dt:eye_num*N_sample*dt-dt;for k=5:50 ss = st(k*N_sample+1:(k+eye_num)*N_sample); drawnow; plot(ttt,ss); hold on;end%plot(ttt,ss);xlabel(t/Ts);ylabel(部分響應(yīng)信號眼圖);例 61%2ASK,2PSK，文件名binarymod.mclear all;close all; A=1;fc = 2; %2Hz;N_sample = 8; N = 500; %碼元數(shù)Ts = 1; %1 baud/s dt = Ts/fc/N_sample; %波形采樣間隔t = 0:dt:N*Ts-dt;Lt = length(t); %產(chǎn)生二進(jìn)制信源d = sign(randn(1,N);dd = sigexpand(d+1)/2,fc*N_sample);gt = ones(1,fc*N_sample); %NRZ波形 figure(1)subplot(221); %輸入NRZ信號波形(單極性）d_NRZ = conv(dd,gt);plot(t,d_NRZ(1:length(t); axis(0 10 0 1.2); ylabel(輸入信號); subplot(222); %輸入NRZ頻譜f,d_NRZf=T2F( t,d_NRZ(1:length(t) );plot(f,10*log10(abs(d_NRZf).2/T);axis(-2 2 -50 10);ylabel(輸入信號功率譜密度(dB/Hz); %2ASK信號ht = A*cos(2*pi*fc*t);s_2ask = d_NRZ(1:Lt).*ht; subplot(223)plot(t,s_2ask);axis(0 10 -1.2 1.2); ylabel(2ASK); f,s_2askf=T2F(t,s_2ask );subplot(224)plot(f,10*log10(abs(s_2askf).2/T);axis(-fc-4 fc+4 -50 10);ylabel(2ASK功率譜密度(dB/Hz); figure(2)%2PSK信號d_2psk = 2*d_NRZ-1;s_2psk = d_2psk(1:Lt).*ht;subplot(221)plot(t,s_2psk);axis(0 10 -1.2 1.2); ylabel(2PSK); subplot(222)f,s_2pskf = T2F(t,s_2psk);plot( f,10*log10(abs(s_2pskf).2/T) );axis(-fc-4 fc+4 -50 10);ylabel(2PSK功率譜密度(dB/Hz); % 2FSK% s_2fsk = Acos(2*pi*fc*t + int(2*d_NRZ-1) ); sd_2fsk = 2*d_NRZ-1; s_2fsk = A*cos(2*pi*fc*t + 2*pi*sd_2fsk(1:length(t).*t );subplot(223)plot(t,s_2fsk);axis(0 10 -1.2 1.2);xlabel(t); ylabel(2FSK)subplot(224)f,s_2fskf = T2F(t,s_2fsk);plot(f,10*log10(abs(s_2fskf).2/T);axis(-fc-4 fc+4 -50 10);xlabel(f);ylabel(2FSK功率譜密度(dB/Hz);例 63%QPSK & OQPSKclear all;close all; M = 4;Ts= 1;fc= 10;N_sample = 16;N_num = 100; dt = 1/fc/N_sample;t = 0:dt:N_num*Ts-dt;T = dt*length(t); py1f = zeros(1,length(t); %功率譜密度1py2f = zeros(1,length(t); %功率譜密度2 for PL=1:100 %輸入100段N_num個(gè)碼字的波形，為了使功率譜密度看起來更加平滑， %可以取這100段信號功率譜密度的平均 d1 = sign(randn(1,N_num); d2 = sign(randn(1,N_num); gt = ones(1,fc*N_sample); %QPSK調(diào)制 s1 = sigexpand(d1,fc*N_sample); s2 = sigexpand(d2,fc*N_sample); b1 = conv(s1,gt); b2 = conv(s2,gt); s1 = b1(1:length(s1); s2 = b2(1:length(s2); st_qpsk = s1.*cos(2*pi*fc*t) - s2.*sin(2*pi*fc*t); s2_delay= -ones(1,N_sample*fc/2) s2(1:end-N_sample*fc/2); st_oqpsk= s1.*cos(2*pi*fc*t) - s2_delay.*sin(2*pi*fc*t); %經(jīng)過帶通后，再經(jīng)過非線性電路 f y1f = T2F(t,st_qpsk); f y2f = T2F(t,st_oqpsk); t y1 = bpf(f,y1f,fc-1/Ts,fc+1/Ts); t y2 = bpf(f,y2f,fc-1/Ts,fc+1/Ts); subplot(221); plot(t,y1); xlabel(t); ylabel(QPSK波形); axis(5 15 -1.6 1.6);title(經(jīng)過帶通后的波形); subplot(222) plot(t,y2); xlabel(t); ylabel(OQPSK波形); axis(5 15 -1.6 1.6);title(經(jīng)過帶通后的波形); %經(jīng)過非線性電路 y1 = 1.5*tanh(2*y1); y2 = 1.5*tanh(2*y2); f y1f = T2F(t,y1); f y2f = T2F(t,y2); py1f = py1f + abs(y1f).