擴頻通信試驗及完整代碼

1、擴頻通信實驗報告題 目:擴頻通信系統(tǒng)仿真指導(dǎo)教師:號: 名: 業(yè):、跳頻通信系統(tǒng)原理介紹跳頻擴頻系統(tǒng)是用偽隨機碼序列構(gòu)成跳頻指令來控制頻率合成器，在多個頻率中進行有選擇的頻移鍵控。與直擴系統(tǒng)相比，調(diào)頻系統(tǒng)中的偽隨機序列并不是 直接傳輸，而是用來選擇信道。調(diào)頻系統(tǒng)的組成框圖如下圖所示：圖中，擴頻調(diào)制器是一個上變頻器，擴頻解調(diào)器是一個下變頻器。頻率合成 器A和頻率合成器B分別為上變頻器和下變頻器提供本振信號， 他們的輸出信號 在調(diào)頻碼的控制下按照統(tǒng)一規(guī)律跳變。二、實驗?zāi)康膶W(xué)習(xí)擴頻通信系統(tǒng)技術(shù)理論基礎(chǔ)及調(diào)頻序列擴頻系統(tǒng)基本原理， 并設(shè)計出跳 頻擴頻通信系統(tǒng)模型。此通信系統(tǒng)具體包括信源模塊、信息調(diào)制模

2、塊、擴頻碼產(chǎn) 生模塊、擴頻模塊、信道模塊、解擴模塊、信息解調(diào)模塊。三、程序設(shè)計流程圖四、仿真環(huán)境本次擴頻通信系統(tǒng)的仿真是用 MATLAB R2012a莫擬實現(xiàn)的，用MATLABS程 來實現(xiàn)對擴頻通信系統(tǒng)的仿真。五、模塊源代碼及仿真波形本系統(tǒng)主要包括信源發(fā)出的基帶信號、發(fā)送端產(chǎn)生的擴頻碼(PN碼)、頻率合成器產(chǎn)生待調(diào)制的載頻信號、FSK調(diào)制、接收端產(chǎn)生的擴頻碼、頻率合成器產(chǎn) 生和發(fā)送端相同的載頻信號、FSK解調(diào)，其中頻率合成器產(chǎn)生的載頻信號頻率受 到擴頻碼的控制，本系統(tǒng)中由頻率合成器產(chǎn)生1000Hz、1050Hz、1150Hz三種頻率的載頻。(1) 調(diào)頻系統(tǒng)調(diào)制模塊A) %產(chǎn)生信源輸出的信息序列

3、(雙極性不歸零碼)Tm=0.25; fm=1/Tm;%碼率u,time=ge nsig(square,2*Tm,E ndTime,Ts);y=2*(u-0.5);figure(1)plot(time,y);title(信源輸岀的信息序列);xlabel( time(sec on ds);axis(0 2 -2 2);信源輸出的信息序列B) % FSK調(diào)制及頻譜T0=0.1; fO=1/TO;T1=0.2; f1=1/T1; uO,time=ge nsig( u1,time=ge nsig( yO=uO.*sig n(-y+1); y1=u1.*sig n(y+1);sinsin,T0,E nd

4、Time,Ts);,T1,E ndTime,Ts);%FSK信號Sig nalFSK=yO+y1;% FSK調(diào)制的頻譜n fft=fs+1;Y = fft(Sig nalFSK, nfft);PSig nalFSK=Y.*conj(Y)/nfft;f=fs*(0: nfft/2)/nfft;figure(2)plot(f,PSig nalFSK(1: nfft/2+1); title(FSK調(diào)制后的頻譜);xlabel(freque ncy (Hz);axis(0 100 -infin f);FSK調(diào)制后的頻譜C) % FSK調(diào)制后，低通濾波cof_low=fir1(64,25/fs);Sig

5、 nalFSK_1=filter(cof_low,1,Sig nalFSK);figure(3)plot(time,Sig nalFSK_1);title(FSK調(diào)制后經(jīng)過低通濾波器的波形)；xlabel(time(sec on ds);axis(0 2 -2 2);YSig nalFSK_ 仁 fft(Sig nalFSK_1, nfft);PSig nalFSK_1 = YSig nalFSK_1.*conj(YSig nalFSK_1)/infft; f = fs*(0: nfft/2)/nfft;figure(4);plot(f,PSig nalFSK_1(1: nfft/2+1);t

6、itle(FSK調(diào)制后經(jīng)過低通濾波的頻譜)；xlabel(freque ncy (Hz);axis(0 100 -infin f);2FSK調(diào)制后經(jīng)過低通濾波器的波形1.510.50-0.5-1-1.5-200.20.40.60.811.21.41.61.8time(sec on ds)FSK調(diào)制后經(jīng)過低通濾波的頻譜6000500040003000200010000102030405060708090100freque ncy (Hz)(2) 混頻模塊%混頻1fc1=1000;Tc=1/fc1;%頻點：1000Carrier,time = gen sig(s in,Tc,E ndTime,Ts

7、);% 產(chǎn)生擴頻載波1MixSig nal 1= Sig nalFSK_1.*Carrier;%混頻2fc2=1050;Tc=1/fc2;%頻點：1050Carrier,time = gen sig(s in,Tc,E ndTime,Ts);% 產(chǎn)生擴頻載波2MixSig nal2=Sig nalFSK_1.*Carrier;%混頻3fc3=1150;Tc=1/fc3;%頻點：1150Carrier,time = gen sig(s in,Tc,E ndTime,Ts);% 產(chǎn)生擴頻載波3MixSig nal3=Sig nalFSK_1.*Carrier;figure(5)plot(time,

8、MixSig nal1,time,MixSig nal2,r ,time,MixSig nal3,k);title(混頻后的波形)；xlabel(time(sec on ds);axis(0 2 -2 2);(3) 帶通濾波cof_ba nd=fir1(64,fc1-12.5,fc1+12.5/fs);yMixSig nal=filter(cof_ba nd,1,MixSig nail);cof_ba nd=fir1(64,fc2-12.5,fc2+12.5/fs);yMixSig nal2=filter(cof_ba nd,1,MixSig nal2);cod_ba nd=fir1(64,f

9、c3-12.5,fc3+12.5/fs);yMixSig nal3=filter(cof_ba nd,1,MixSig nal3);figure(6)plot(time,yMixSig nal,time,yMixSig nal2,r ,time,yMixSig nal3,k);title(經(jīng)過帶通濾波的混頻信號)；xlabel(time(sec on ds);axis(0 2 -2 2);經(jīng)過帶通濾波的混頻信號2tItitict1.5 -1-1-1.5 -2 tJlI:00.20.40.60.811.21.41.61.82time(sec on ds)(4) 解擴模塊A) %瀨收端解擴fc=1

10、000;Tc=1/fc;Carrier,time=ge nsig(si n,Tc,E ndTime,Ts);%產(chǎn)生擴頻載波Sig n_rec=Sig n_send;ySig n_rec=Sig n_rec.*Carrier;figure(8);plot(time,ySig n_rec);title(解擴后的信號);xlabel(time(sec on d);axis(0 2 -1 1);1解擴后的信號0.80.60.40.20-0.2-0.4-0.6-0.8 f廠-1 Lttjlci-00.20.40.60.811.21.41.61.82time(sec ond)B) %低通濾波，取下邊頻yr

11、r=ySig n_rec; cof_low=fir1(64,25/fs);Sig n_rec_1=filter(cof_low,1,ySig n_rec);figure(9);plot(time,Sig n_rec_1);title(解擴后的下邊頻的信號);xlabel(time(sec on ds);axis(0 2 -1 1);YSign_rec_ 仁 fft(Sign_rec_1, nfft);PSign_rec_ 1=YSign_rec_1.*conj(YSign_rec_1)/nfft; f=fs*(0: nfft/2)/nfft;figure(10); plot(f,PSign_r

12、ec_1(1: nfft/2+1);title(解擴后的下邊頻頻譜)；xlabel( freque ncy(Hz);axis(0 100 -infin f);解擴后的下邊頻的信號C) % FSK解碼 cof_f0=fir1(64,f0-0.25,f0+0.25/fs); cof_f仁fir1(64,f1-0.25,f1+0.25/fs);DeFSKO=filter(cof_fO,1,Sign_rec_1);抽樣判決前的信號DeFSK1=filter(cof_f1,1,Sign_rec_1);rDeFSKO=DeFSKO.*uO;rDeFSK1=DeFSK1.*u1;rDeFSK=rDeFSK0

13、-rDeFSK1;figure(11);plot(time,rDeFSK);title(抽樣判決前的信號);xlabel( time (sec on ds);axis(0 2 -2 2);21.510.50-0.5-1-1.5-200.20.40.60.811.21.41.61.82time (sec on ds)D) %抽樣判決Sampletime=0.25/Ts;Message=;Num=0;while (Num2/Ts)if (mod(Num,Sampletime)=0)Message=Messageon es(1,Sampletime+1)*sig n( sum(rDeFSK(Num+

14、1):(Num+Sampletime);endNum=Num+Sampletime;endfigure(12);plot(1:le ngth(Message)/fs,Message);title(輸岀端恢復(fù)的信息); xlabel( time(sec on ds);axis(0 2 -2 2);輸出端恢復(fù)的信息2(Ici1.5 -1 -0.5 -0 -0.5 -1-1.5 -1.6 1.8 2-2 LJCL-00.20.40.60.811.21.4time(sec on ds)六、附錄(完整源代碼)clcclear all% 調(diào)頻通信過程%給出三個頻點，濾波后僅對第一個頻點進行解擴 %初始化T

15、s=0.00001;fs=1/Ts;En dTime=2-Ts; %2s%產(chǎn)生信源輸出的信息序列(雙極性不歸零碼)Tm=0.25; fm=1/Tm;%碼率u,time=ge nsig(square,2*Tm,E ndTime,Ts);y=2*(u-0.5);figure(1)plot(time,y);title(信源輸岀的信息序列)；);xlabel( time(seconds) axis(0 2 -2 2);% FSK 調(diào)制 T0=0.1; f0=1/T0;T1=0.2; f1=1/T1;u0,time=gensig(u1,time=gensig(sinsin,T0,EndTime,Ts);

16、,T1,EndTime,Ts);y0=u0.*sign(-y+1); y1=u1.*sign(y+1);SignalFSK=y0+y1;%FSK 信號% FSK 調(diào)制的頻譜 nfft=fs+1;Y = fft(SignalFSK,nfft); PSignalFSK=Y.*conj(Y)/nfft; f=fs*(0:nfft/2)/nfft;figure(2) plot(f,PSignalFSK(1:nfft/2+1); title( FSK 調(diào)制后的頻譜 ); xlabel( frequency (Hz) ); axis(0 100 -inf inf);% FSK 調(diào)制后，低通濾波 cof_l

17、ow=fir1(64,25/fs);SignalFSK_1=filter(cof_low,1,SignalFSK); figure(3)plot(time,SignalFSK_1);title( FSK 調(diào)制后經(jīng)過低通濾波器的波形 ); xlabel( time(seconds) );axis(0 2 -2 2);YSignalFSK_1= fft(SignalFSK_1,nfft);PSignalFSK_1 = YSignalFSK_1.*conj(YSignalFSK_1)/nfft; f = fs*(0:nfft/2)/nfft;figure(4); plot(f,PSignalFSK_

18、1(1:nfft/2+1); title( FSK 調(diào)制后經(jīng)過低通濾波的頻譜 ); xlabel( frequency (Hz) );axis(0 100 -inf inf);%混頻 1fc1=1000;Tc=1/fc1;%頻點： 1000%產(chǎn)生擴頻載波 1Carrier,time = gensig( sin ,Tc,EndTime,Ts);MixSignal1=SignalFSK_1.*Carrier;%混頻 2fc2=1050;Tc=1/fc2;%頻點：1050Carrier,time = gensig(sin,Tc,EndTime,Ts);%產(chǎn)生擴頻載波 2MixSignal2=Sign

19、alFSK_1.*Carrier;%混頻 3fc3=1150;Tc=1/fc3;%頻點：1150Carrier,time = gensig(sin,Tc,EndTime,Ts);%產(chǎn)生擴頻載波 3MixSignal3=SignalFSK_1.*Carrier;);figure(5) plot(time,MixSignal1,time,MixSignal2, r ,time,MixSignal3, k title( 混頻后的波形 );xlabel( time(seconds) );axis(0 2 -2 2);% 帶通濾波 cof_band=fir1(64,fc1-12.5,fc1+12.5/f

20、s);yMixSignal=filter(cof_band,1,MixSignal1); cof_band=fir1(64,fc2-12.5,fc2+12.5/fs);yMixSignal2=filter(cof_band,1,MixSignal2); cod_band=fir1(64,fc3-12.5,fc3+12.5/fs);yMixSignal3=filter(cof_band,1,MixSignal3);k );figure(6) plot(time,yMixSignal,time,yMixSignal2, r ,time,yMixSignal3, title( 經(jīng)過帶通濾波的混頻信號

21、 );xlabel( time(seconds) ); axis(0 2 -2 2);% 傳輸信道 Sign_send=yMixSignal;sin ,Tc,EndTime,Ts);%產(chǎn)生擴頻載波%接收端解擴 fc=1000;Tc=1/fc; Carrier,time=gensig( ySign_rec=Sign_rec.*Carrier;figure(8);plot(time,ySign_rec); title( 解擴后的信號 ); xlabel( time(second) );axis(0 2 -1 1);% 低通濾波，取下邊頻 yrr=ySign_rec; cof_low=fir1(64,25/fs);Sign_rec_1=filter(cof_low,1,ySign_rec);figure(9); plot(time,Sign_rec_1);title( 解擴后的下邊頻的信號 ); xlabel( time(seconds) ); axis(0 2 -1 1);YSign_rec_1=fft(Sign_rec_1,nfft); PSign_rec_1=YSign_rec_1.*conj(YSign_rec_1)/nfft; f=fs