數(shù)字通信QAM調(diào)制及其MATLAB仿真程序

1、數(shù)字通信QAM調(diào)制及其MATLA仿真程序1. %數(shù)字通信QAM仿真2. clear3. %產(chǎn)生基帶符號(hào)流4. M=16;%進(jìn)制16QAM5。N=40;%信源比特流長(zhǎng)度，為保證對(duì)齊，選擇是log2(M)的整倍數(shù)6bitstream=zeros(1,N);7 symbolstream=zeros(1,N/log2(M);8 ,forn1=1:N9bitstream(n1)=binornd(1,0.5,1,1);10.end%格雷碼編碼12forn1=1:length(symbolstream)1pack=bitstream(4*(n1-1)+1)bitstream(4*(n1-1)+2)bitst

2、ream(4*(n1-1)+3)bitstream(4*(n1-1)+4);14 ifpack=000015 .symbolstream(n1)=1+j;16elseifpack=00101symbolstream(n1)=2+j;elseifpack=0011-|q.,symbolstream(n1)=2+2j;elseifpack=0001lsymbolstream(n1)=1+2j;elseifpack=010123. -symbolstream(n1)=-1+2j;24. elseifpack=010025. symbolstream(n1)=-1+j;26. elseifpack=0

3、111symbolstream(n1)=-2+2j;elseifpack=0110symbolstream(n1)=-2+j;elseifpack=1110symbolstream(n1)=-2-j;31.32.33.34.35.36.37.38.39.40.41.42.elseifpack=1111symbolstream(n1)=-2-2j;elseifpack=1101symbolstream(n1)=-1-2j;elseifpack=1100symbolstream(n1)=1-j;elseifpack=1000symbolstream(n1)=1-j;elseifpack=1010s

4、ymbolstream(n1)=2-j;elseifpack=100143.symbolstream(n1)=1-2j;44.elsesymbolstream(n1)=2-2j;endendfigure(1)holdonforn1=-2:245.forn2=-2:246.if(nfc=0)|(n2=0)scatter(n1,n2);47. end48. end49. end50. axis(-33-33);51. holdoff52. title6QAM星座圖)；53. xlabel(同相支路)54.ylabel(正交支路)55.%產(chǎn)生載波56.fc=10；%載波頻率57.58.59.60.6

5、1.62.63. fs=100;%采樣頻率64. T=1;%每符號(hào)持續(xù)時(shí)間65. N_samples=T*fs;%每符號(hào)內(nèi)的采樣點(diǎn)數(shù)66. t=O:T/N_samples:(T-T/N_samples);67. carrier=exp(j*2*pi*fc*t);68. %產(chǎn)生信號(hào)脈沖g(t)69. %gt=ones(1Jength(carrier);70. gt=1-cos(2*pi*(1/T)*t);71.72. %生成調(diào)制信號(hào)S(t)73. St_complex=zeros(1,length(carrier)*length(symbolstream);74. forn1=1:length(

6、symbolstream)75. St_complex(N_samples*(n1-1)+1):(N_samples*(n1-1)+N_samples)=(symbolstream(n1)*carrier).*gt;76. end77. figure(2)78. St_real=real(St_complex);79. plot(St_real)80. title(QAM仿真波形圖載波10Hzg(t)為升余弦脈沖)；81. xlabe(采樣點(diǎn))82. ylabel(幅度)83. %求出功率譜，這種功率譜不是按照公式直接計(jì)算的，而是對(duì)所產(chǎn)生的一段時(shí)間內(nèi)的信號(hào)的采樣點(diǎn)進(jìn)行FFT所得到的84. sp

7、ectrum=(real(fft(St_real,10*length(St_real).A2;85. S_spectrum=spectrum(1:length(spectrum)/2);86. figure(3)87. F=0:fs/(2*length(S_spectrum):fs/2-fs/(2*length(S_spectrum);88. plot(F,10*log10(S_spectrum)89. axis(050-7060);90. 也le(QAM信號(hào)功率譜密度)91. xlabel(頻率/Hz)92. ylabel（功率）93. figure(4)94. index=400:1600;95. plot(