數(shù)字通信QAM調(diào)制及其MATLAB仿真程序

1、1.2.3.4.5.6.7.8.9.10.11.12.13.14.15.16.17.18.19.20.21.22.23.24.25.26.27.28.29.30.數(shù)字通信QAM調(diào)制及其MATLA仿真程序%數(shù)字通信QAM仿真clear%產(chǎn)生基帶符號流M=16;% 進制 16QAMN=40;%信源比特流長度，為保證對齊，選擇是log2(M)的整倍數(shù)bitstream=zeros(1,N);symbolstream=zeros(1,N/log2(M);for n1=1:Nbitstream(n1)=binornd(1,0.5,1,1);end%格雷碼編碼for n1=1:length(symbols

2、tream)pack=bitstream(4*(n1-1)+1) bitstream(4*(n1-1)+2) bitstream(4*(n1-1)+3) bitstream(4*(n1-1)+4);if pack=0 0 0 0symbolstream(n1)=1+j;elseif pack=0 0 1 0symbolstream(n1)=2+j;elseif pack=0 0 1 1symbolstream(n1)=2+2j;elseif pack=0 0 0 1symbolstream(n1)=1+2j;elseif pack=0 1 0 1symbolstream(n1)=-1+2j;e

3、lseif pack=0 1 0 0symbolstream(n1)=-1+j;elseif pack=0 1 1 1symbolstream(n1)=-2+2j;elseif pack=0 1 1 0symbolstream(n1)=-2+j;elseif pack=1 1 1 031.32.33.34.35.36.37.38.39.40.41.42.43.44.45.46.47.48.49.50.51.52.53.54.55.56.57.58.59.60.61.62.symbolstream(n1)=-2-j;elseif pack=1 1 1 1symbolstream(n1)=-2-2

4、j;elseif pack=1 1 0 1symbolstream(n1)=-1-2j;elseif pack=1 1 0 0symbolstream(n1)=-1-j;elseif pack=1 0 0 0symbolstream(n1)=1-j;elseif pack=1 0 1 0symbolstream(n1)=2-j;elseif pack=1 0 0 1symbolstream(n1)=1-2j;else symbolstream(n1)=2-2j; end end figure(1) hold on for n1=-2:2for n2=-2:2if (n 仁=0)|(n2=0)

5、scatter(n1,n2);endendendaxis(-3 3 -3 3);hold offtitle('16QAM 星座圖');xlabel('同相支路')ylabel('正交支路')%產(chǎn)生載波fc=10;%載波頻率63. fs=100;%采樣頻率64. T=1;%每符號持續(xù)時間65. N_samples=T*fs; %每符號內(nèi)的采樣點數(shù)66. t=0:T/N_samples:(T-T/N_samples);67. carrier=exp(j*2*pi*fc*t);68. %產(chǎn)生信號脈沖g(t)69. %gt=ones(1,length(c

6、arrier);70. gt=1-cos(2*pi*(1/T)*t);71.71. %生成調(diào)制信號S(t)72. St_complex=zeros(1,length(carrier)*length(symbolstream);73. for n1=1:length(symbolstream)74. St_complex(N_samples*(n1-1)+1):(N_samples*(n1-1)+N_samples)=(symbolstream(n1)*carrier).* gt;75. end76. figure(2)77. St_real=real(St_complex);78. plot(

7、St_real)79. title('QAM仿真波形圖 載波10Hz g(t)為升余弦脈沖');80. xlabel('采樣點')81. ylabel('幅度')82. %求岀功率譜，這種功率譜不是按照公式直接計算的，而是對所產(chǎn)生的一段時間內(nèi)的信號的采樣點 進行FFT所得到的83. spectrum=(real(fft(St_real,10*length(St_real).A2;84. S_spectrum=spectrum(1:length(spectrum)/2);85. figure(3)86. F=0:fs/(2*length(S_spectrum):fs/2-fs/(2*length(S_spectrum);87. plot(F,10*log10(S_spectrum)88. axis(0 50 -70 60);89. title('QAM 信號功率譜密度')90. xlabel('頻率 /Hz')91. ylabel('功率')92. figure(4)93. index=400:1600;94. plot(F(index),10*log10(S_spect