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1、一仿真要求：f= （0.0000+1i*0.0000,0.0485+1i*0.0194,0.0573+1i*0.0253, 0.0786+1i*0.0282,0.0874+1i*0.0447,0.9222+1i*0.0301,0.1427+1i*0.0349,0.0835+1i*0.0157,0.0621+1i*0.0078,0.0359+1i*0.0049,0.0214+1i*0.0019）1. 研究信道的幅度谱(单位dB)，画出频谱图。2. 设计K=1(2k+1=3)及K=10(2K+1=21)的MMSE均衡器。3. 设计K=1(2k+1=3)及K=10(2K+1=21)的ZF均衡器(迫零
2、均衡器)。4. 画出以上均衡器的频谱图及等效信道频谱。5. 分析总结。二实验原理：均衡器通信系统中，是用来校正传输信道幅度频率特性和相位频率特性的部件。将频率为f的正弦波放入传输信道，输出电压与输入电压的幅度比随f变化的特性称为频率特性，简称幅频特性；输出电压与输入电压的相位差随f变化的特性称为相位频率特性，简称相频特性。各种传输信道所传输的信号，一般有一些不同频率的分量组成。在信号频带范围内，若信道的幅频特性是恒定值；相位；随f变化的特性是直线。可写成C(f)=2ft+，t为常数；(称为相截)等于n，n=0，2，4，则信号波形经传输不产生畸变。条件使不同频率分量经传输后有相同的输出输入幅度比
3、，条件、使其有相同的时间延迟。但实际通信常不符合上诉条件，因而信号产生畸变。若畸变超过允许量，则要用均衡器对信号特性进行校正。由于实际的限带信道的传递函数往往是非理想的，且经常是时变的、未知的，因而系统特性不符合奈窐斯特准则，导致在接受端抽样时刻存在码间干扰，使得系统误码性能下降。为此，要考虑在信道传递函数是非理想情况，且信号在信道传输中受到加性白高斯噪声干扰条件下的接收机的设计问题。在限带数字通信系统中所采取的技术之一是在收端抽样、判决之前加一均衡器，此均衡器是用来补偿信道特性的不完善，从而减小在收端抽样时刻的码间干扰。图2.1 具有均衡器的数字基带传输系统均衡器通常是用滤波器来实现的，使用
4、滤波器来补偿失真的脉冲，判决器得到的解调输出样本，是经过均衡器修正过的或者清除了码间干扰之后的样本。自适应均衡器直接从传输的实际数字信号中根据某种算法不断调整增益，因而能适应信号的随机变化，使均衡器总是保持最佳的状态，从而有更好的失真补偿性能。信道均衡技术大致分为两大类：线性均衡和非线性均衡。在信道频率响应特性比较平坦、所引起的码间干扰不太严重的情况下，可采用线性均衡。线性均衡器可用横向滤波器实现，图示如下：图2.2 横向滤波器结构三仿真结果：1.研究信道的幅度谱(单位dB)，画出频谱图。clcf=0.0000+1i*0.0000,0.0485+1i*0.0194,0.0573+1i*0.02
5、53, 0.0786+1i*0.0282,0.0874+1i*0.0447,0.9222+1i*0.0301,0.1427+1i*0.0349,0.0835+1i*0.0157,0.0621+1i*0.0078,0.0359+1i*0.0049,0.0214+1i*0.0019;N=64;y1=fft(f,N);y2=abs(y1);x=(0:N-1)*(10/(N-1); % w/(2*pi)y=10*log10(y2);plot(x,y);xlabel(k);ylabel(F(e(jwT)| (dB);title(幅度谱F(e(jwT);grid on 图3.1 幅度谱2. 设计K=1(2
6、k+1=3)及K=10(2K+1=21)的MMSE均衡器(迫零均衡器)。2.1 K=1(2K+1=3)的MMSE均衡器：f=0.0000+j*0.0000,0.0485+j*0.0194,0.0573+j*0.0253,0.0786+j*0.0282,0.0874+j*0.0447,0.9222+j*0.0301,0.1427+j*0.0349,0.0835+j*0.0157,0.0621+j*0.0078,0.0359+j*0.0049,0.0214+j*0.0019;N0=0;f2=N0*eye(3);f3=N0*eye(21);m=conv(conj(f),fliplr(f);f1=m(
7、11), m(12), m(13); m(12) ,m(11), m(12) ;m(13) m(12) m(11) ;r=m(11:21) zeros(1,10);c=m(11:-1:1) zeros(1,10);f4=toeplitz(r,c);F1=f1+f2;q1=f(7),f(6),f(5);Cop3=F1*q1;Cop3 Cop3 = 0.3776 + 0.0592i 0.8955 + 0.0499i 0.3379 + 0.0672i2.2 K=10(2K+1=21)的MMSE均衡器：f=0.0000+j*0.0000,0.0485+j*0.0194,0.0573+j*0.0253,
8、0.0786+j*0.0282,0.0874+j*0.0447,0.9222+j*0.0301,0.1427+j*0.0349,0.0835+j*0.0157,0.0621+j*0.0078,0.0359+j*0.0049,0.0214+j*0.0019;N0=0;f2=N0*eye(3);f3=N0*eye(21);m=conv(conj(f),fliplr(f);f1=m(11), m(12), m(13); m(12) ,m(11), m(12) ;m(13) m(12) m(11) ;r=m(11:21) zeros(1,10);c=m(11:-1:1) zeros(1,10);f4=
9、toeplitz(r,c);F21=f3+f4;q2=0,0,0,0,0,conj(f(11),conj(f(10),conj(f(9),conj(f(8),conj(f(7),conj(f(6),conj(f(5),conj(f(4),conj(f(3),conj(f(2),conj(f(1),0,0,0,0,0;Cop21=F21*q2;Cop21 Cop21 = 0.0023 - 0.0002i 0.0067 - 0.0006i 0.0147 - 0.0010i 0.0283 - 0.0015i 0.0494 - 0.0011i 0.1082 + 0.0030i 0.1925 - 0.0
10、018i 0.2656 + 0.0066i 0.3375 + 0.0243i 0.4397 + 0.0503i 0.9547 + 0.0637i 0.3963 + 0.0854i 0.3222 + 0.0788i 0.2502 + 0.0757i 0.1865 + 0.0620i 0.0816 + 0.0287i 0.0408 + 0.0199i 0.0231 + 0.0120i 0.0114 + 0.0063i 0.0043 + 0.0024i 0.0012 + 0.0009iclcclear allclose allf=0.0000+j*0.0000,0.0485+j*0.0194,0.0
11、573+j*0.0253,0.0786+j*0.0282,0.0874+j*0.0447,0.9222+j*0.0301,0.1427+j*0.0349,0.0835+j*0.0157,0.0621+j*0.0078,0.0359+j*0.0049,0.0214+j*0.0019;N0=0;f2=N0*eye(3);f3=N0*eye(21);m=conv(conj(f),fliplr(f);f1=m(11), m(10), m(9); m(12) ,m(11), m(10) ;m(13) m(12) m(11) ;r=m(11:21) zeros(1,10);c=m(11:-1:1) zer
12、os(1,10);f4=toeplitz(r,c);F1=f1+f2;F2=f3+f4;q1=f(7),f(6),f(5);q2=0,0,0,0,0,conj(f(11),conj(f(10),conj(f(9),conj(f(8),conj(f(7),conj(f(6),conj(f(5),conj(f(4),conj(f(3),conj(f(2),conj(f(1),0,0,0,0,0;a1=F1q1;a2=F2q2;N=64;fs=10;x=(0:N-1)*fs/N;A1=fft(a1,N);A2=fft(a2,N);B1=abs(A1);B2=abs(A2);C1=10*log10(B
13、1);C2=10*log10(B2);plot(x,C1,or);text(6,2.5,三抽头MMSE均衡器);xlabel(wT);ylabel(10log10|F(ejwT)| (dB);hold onplot(x,C2,dg);text(3,0.8,二十一抽头MMSE均衡器);title(MMSE均衡器);图3.2 MMSE均衡器3.设计K=1(2k+1=3)及K=10(2K+1=21)的ZF均衡器。3.1 K=1的ZF均衡器：f=0.0000+1i*0.0000,0.0485+1i*0.0194,0.0573+1i*0.0253, 0.0786+1i*0.0282,0.0874+1i*
14、0.0447,0.9222+1i*0.0301,0.1427+1i*0.0349,0.0835+1i*0.0157,0.0621+1i*0.0078,0.0359+1i*0.0049,0.0214+1i*0.0019;q3=0;1;0;A=f(6),f(5),f(4);f(7),f(6),f(5);f(8),f(7),f(6);F=inv(A);Cop3=F*q3;Cop3首先得到：F = 1.1043 - 0.0227i -0.0942 - 0.0418i -0.0886 - 0.0204i -0.1656 - 0.0289i 1.1112 - 0.0155i -0.0942 - 0.041
15、8i -0.0759 - 0.0035i -0.1656 - 0.0289i 1.1043 - 0.0227i然后得到：Cop3 = -0.0942 - 0.0418i 1.1112 - 0.0155i -0.1656 - 0.0289i得出：3.2 K=10的ZF均衡器：f=0.0000+1i*0.0000,0.0485+1i*0.0194,0.0573+1i*0.0253, 0.0786+1i*0.0282,0.0874+1i*0.0447,0.9222+1i*0.0301,0.1427+1i*0.0349,0.0835+1i*0.0157,0.0621+1i*0.0078,0.0359+1i*0.0049,0.0214+1i*0.0019;
