課程設(shè)計報告——matlab瑞利衰落信道仿真

1、目錄摘要 ·················································&

2、#183;·················································&

3、#183;························· 11、設(shè)計原理 ······················

4、3;·················································

5、3;······································ 21.1設(shè)計目的 ··········

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8、· 21.2仿真原理 ···············································&#

9、183;·················································&#

10、183;············· 21.2.1瑞利分布簡介 ··································

11、··················································

12、········· 21.2.2多徑衰落信道基本模型 ······································

13、······································· 21.2.3產(chǎn)生服從瑞利分布的路徑衰落r(t) ·······

14、;··················································

15、;··· 31.2.4產(chǎn)生多徑延時 ············································

16、83;················································ 41.3仿真框架

17、 ··················································

18、;··················································

19、;··········· 42、設(shè)計任務(wù) ·····································&#

20、183;·················································&#

21、183;······················· 42.1設(shè)計任務(wù)要求 ························&#

22、183;·················································&#

23、183;···························· 42.2 MATLAB 仿真程序要求 ··················

24、··················································

25、················ 43、DSB調(diào)制解調(diào)分析的MATLAB實現(xiàn) ······························&

26、#183;································ 53.1 DSB調(diào)制解調(diào)的MATLAB實現(xiàn) ·············&#

27、183;·················································&#

28、183;········ 53.2瑞利衰落信道的MATLAB實現(xiàn) ······································

29、;··································· 64、模擬仿真及結(jié)果分析 ············

30、83;·················································

31、83;···························· 74.1模擬仿真 ····················

32、;··················································

33、;········································· 74.1.1多普勒濾波器的頻響 ······

34、··················································

35、································ 74.1.2多普勒濾波器的統(tǒng)計特性 ···············

36、;··················································

37、;··············· 74.1.3信道的時域輸入/輸出波形 ·······························

38、83;··············································· 84.2仿真結(jié)果分析

39、83;·················································

40、83;·················································

41、83;·· 84.2.1時域輸入/輸出波形分析 ············································&#

42、183;······································ 84.2.2頻域波形分析 ·········

43、··················································

44、········································· 84.2.3多普勒濾波器的統(tǒng)計特性分析 ·····

45、83;·················································

46、83;················ 95、小結(jié)與體會 ································

47、;··················································

48、;························· 96、參考文獻 ·······················&#

49、183;·················································&#

50、183;····································· 9MATLAB 通信仿真設(shè)計摘要主要運用MATLAB進行編程，實現(xiàn)采用對輸入信號進行抑制載波的雙邊帶調(diào)幅；而后將調(diào)幅波輸入信道，研究多徑信道的特性

51、對通信質(zhì)量的影響；最后將信道內(nèi)輸出的條幅波進行同步解調(diào)，解調(diào)出與輸入信號波形相類似的波形，觀測兩者差別。同時輸出多普勒濾波器的統(tǒng)計特性圖及信號時域和頻域的輸入、輸出波形。關(guān)鍵字：雙邊帶調(diào)幅瑞利衰落相干解調(diào)MATLAB1、 設(shè)計原理1.1設(shè)計目的由于多徑和移動臺運動等影響因素，使得移動信道對傳輸信號在時間、頻率和角度上造成了色散，如時間色散、頻率色散、角度色散等等，因此多徑信道的特性對通信質(zhì)量有著至關(guān)重要的影響，而多徑信道的包絡(luò)統(tǒng)計特性成為我們研究的焦點。根據(jù)不同無線環(huán)境，接收信號包絡(luò)一般服從幾種典型分布，如瑞利分布、萊斯分布和Nakagami-m分布。在設(shè)計中，專門針對服從瑞利分布的多徑信道進

52、行模擬仿真，進一步加深對多徑信道特性的了解。1.2仿真原理1.2.1瑞利分布簡介（1）環(huán)境條件：通常在離基站較遠、反射物較多的地區(qū)，發(fā)射機和接收機之間沒有直射波路徑，存在大量反射波；到達接收天線的方向角隨機且在（02）均勻分布；各反射波的幅度和相位都統(tǒng)計獨立。（2）幅度、相位的分布特性：包絡(luò) r 服從瑞利分布，在02內(nèi)服從均勻分布。瑞利分布的概率分布密度如圖1所示：圖1 瑞利分布的概率分布密度 1.2.2多徑衰落信道基本模型根據(jù)ITU-RM.1125標(biāo)準(zhǔn)，離散多徑衰落信道模型為 (1)其中復(fù)路徑衰落，服從瑞利分布； 是多徑時延。多徑衰落信道模型框圖如圖2所示：圖2 多徑衰落信道模型框圖1.2.

53、3產(chǎn)生服從瑞利分布的路徑衰落r(t)利用窄帶高斯過程的特性，其振幅服從瑞利分布，即 （2）上式中，、分別為窄帶高斯過程的同相和正交支路的基帶信號。首先產(chǎn)生獨立的復(fù)高斯噪聲的樣本，并經(jīng)過FFT后形成頻域的樣本，然后與S（f）開方后的值相乘，以獲得滿足多普勒頻譜特性要求的信號，經(jīng)IFFT后變換成時域波形，再經(jīng)過平方，將兩路的信號相加并進行開方運算后，形成瑞利衰落的信號r(t)。如下圖3所示:圖3 瑞利衰落的產(chǎn)生示意圖其中， （3）1.2.4產(chǎn)生多徑延時多徑/延時參數(shù)如表1所示：表1 多徑延時參數(shù)TapRelative delay (ns)Average power (dB)1002310-1.03

54、710-9.041 090-10.051 730-15.062 510-20.01.3仿真框架根據(jù)多徑衰落信道模型（見圖2），利用瑞利分布的路徑衰落（見圖3）和多徑延時參數(shù)（見表1），我們可以得到多徑信道的仿真框圖，如圖4所示：圖4 多徑信道的仿真框圖2、 設(shè)計任務(wù) 2.1設(shè)計任務(wù)要求（1）查找資料，了解瑞利衰落信道模型的分類，結(jié)合某種模型，掌握瑞利分布的多徑信道仿真原理，用MATLAB仿真實現(xiàn)瑞利分布的多徑信道的仿真；（2）根據(jù)已學(xué)的知識，實現(xiàn)一種基帶信號的模擬調(diào)制并做出仿真；（3）結(jié)合（1）（2）步，觀察已調(diào)信號通過瑞利信道后的時域波形圖和頻譜圖；（4）對仿真結(jié)果做適當(dāng)分析。2.2 MAT

55、LAB 仿真程序要求（1）參數(shù)設(shè)計準(zhǔn)確、合理；（2）關(guān)鍵語句加注釋；（3）仿真結(jié)果正確，圖形清晰。3、DSB調(diào)制解調(diào)分析的MATLAB實現(xiàn)3.1 DSB調(diào)制解調(diào)的MATLAB實現(xiàn)%main.mclc;LengthOfSignal=10000; %信號長度fm=500; %最大多普勒頻移？相關(guān)文獻應(yīng)該有估算公式fc=5000; %信道載波頻率t=1:LengthOfSignal; % SignalInput=sin(t/100);%DSB調(diào)制SignalInput=sin(t/50);%+cos(t/65); %調(diào)制信號c=cos(0.2*pi*t);%載波信號 y_in=SignalInput

56、.*c;%調(diào)制delay=0 31 71 109 173 251;%10nspower=0 -1 -9 -10 -15 -20; %dBy_in=zeros(1,delay(6) y_in; %為時移補零y_out=zeros(1,LengthOfSignal); %存放經(jīng)信道未解調(diào)的信號（現(xiàn)為無輸入信號%時的輸出信號）%y_out_end最終解調(diào)后信號%多路徑衰落for i=1:6%圖4 f=1:2*fm-1; Rayl; y_out=y_out+r.*y_in(delay(6)+1-delay(i):(delay(6)+LengthOfSignal-delay(i)*10(power(i)

57、/20);end;% S(t)*cos(w*t)=m(t)*cos(w*t)*cos(w*t)=0.5*m(t)*(1+cos(2*w*t)%用一個低通濾波器將上式中的第一項和第二項分離，無失真的恢復(fù)出原始的調(diào)制信號。%這種調(diào)制方法又稱為同步解調(diào)或相干解調(diào)%同步解調(diào)y_out_end=y_out.*c;%同步解調(diào)或相干解調(diào)%低通濾波wp=0.1*pi;ws=0.12*pi;Rp=1;As=15;N,wn=buttord(wp/pi,ws/pi,Rp,As);b,a=butter(N,wn);y_out_end =filter(b,a,y_out_end);%濾波y_out_end =2* y_

58、out_end;%恢復(fù)幅度%原信號的頻譜K=fft(SignalInput);%DSB調(diào)制后信號的頻譜L=fft(y_in);%y_out的頻譜（含包絡(luò)）M=fft(y_out);%最終解調(diào)的頻譜N=fft(y_out_end);%輸出 figure(1);subplot(4,2,1);plot(SignalInput(delay(6)+1:LengthOfSignal);axis(0,3000,-2,2);title('原始輸入信號');subplot(4,2,2);plot(abs(fftshift(K); axis(4900,5100,0,6000);title('

59、;原始輸入信號的頻譜 ');subplot(4,2,3);plot(y_in(delay(6)+1:LengthOfSignal);axis(0,3000,-2,2); %去除時延造成的空白信號title(' 進入瑞利信道前，DSB調(diào)制后的信號');subplot(4,2,4);plot(abs(fftshift(L); axis(3500,6500,0,3000);title('進入瑞利信道前，DSB調(diào)制后的信號的頻譜 ');subplot(4,2,5);plot(y_out(delay(6)+1:LengthOfSignal);axis(0,3000,-0.08,0.08); %去除時延造成的空白信號title('經(jīng)瑞利信道后，DSB解調(diào)前的信號');subplot(4,2,6);plot(abs(fftshift(M);axis(3500,6500,0,100);title('經(jīng)瑞利信道后，DSB解調(diào)前的信號的頻譜');subplot(4,2,7);plot(y_out_end(delay(6)+1:LengthOfSi