基于MATLAB的单边带电台仿真

1、单边带电台仿真单边带电台仿真设计要求设计要求1：完成系统模型设计，包括发送模块，信道模块，接收模块2：三种本地载波分别作相干解调。3：比较三种结果，分析本地载波频率误差对解调话音质量的影响。设计参数设计参数1）输入话音信号，采样频率8000Hz，话音预滤波是300,3400Hz的带通滤波器；2）载波频率：10kHz；调制输出上边带；3）信道：带限高斯噪声信道，10,13.5kHz；加入的噪声可调；4）接收机：想干解调；本地载波分别为：9.8KHz,9.8KHz,9.8KHz;5)解调滤波器;300,3400Hz的带通滤波器。发送模块发送模块发送模块需要完成：1,采样频率8000Hz，预滤波30

2、0,34002,10KHz单边带调制输出上边带发送模块发送模块%FileName:ForSSB.mclc;clear all;%功能，采样点数40000，采样率为8000%jilu = wavrecord(5*8000, 8000, double);%wavwrite(jilu, GDGvoice8000.wav);wav, fs = wavread(GDGvoice8000.wav);%计算声音时间长度t_end = 1/fs * length(wav);%仿真系统采样时间点Fs = 50000;t = 1/Fs:1/Fs:t_end;%设计3003400hz的带通滤波器fenzi, fen

3、mu = butter(3, 300 3400/(fs/2);%对音频信号进行滤波wav = filter(fenzi, fenmu, wav);%输出滤波后的声音wavwrite(wav, LVBO_OUT.wav);%利用插值函数将音频的采样率提升为50khzwav = interp1(1/fs:1/fs:t_end, wav, t, spline);%音频信号的希尔伯特变换wav_hilbert = imag(hilbert(wav);%载波频率fc = 10000;%单边带调制SSB_OUT = wav.*cos(2*pi*fc*t) - wav_hilbert.*sin(2*pi*f

4、c*t);%输出波形figure(1);信道模块信道模块%FileName:ForSNB.m%功能;计算实际信噪比%clear;in, Fs = wavread(SSB_OUT.wav);%设定信噪比为20时的新到输出SNR_db = 20;out = ChanelSimulink(in, SNR_db);wavwrite(out, Fs, Chanel_OUT.wav);%FileName:ChanelSimulink.mfunction out = ChanelSimulink(in, SNR_db)% SNR_db 设定信噪比% in 输入信号序列% out 信道输出序列% 系统采样率F

5、s = 50000;Power_of_in = var(in);Power_of_noise = Power_of_in/(10.(SNR_db/10);% 信道带宽bandwidth = 13500 - 10000;% 噪声功率谱密度值 W/HzNO = Power_of_noise/bandwidth;Gause_noise = sqrt(NO*Fs/2) .* randn(size(in);% 噪声通道 1013.5kHznum, den = butter(4, 10000 13500/(Fs/2);signal_of_filter_out = filter(num, den, in);

6、noise_of_filter_out = filter(num, den, Gause_noise);SNR_dB = 10*log10(var(signal_of_filter_out)/var(noise_of_filter_out);% 测量得出信噪比% 信道输出out = signal_of_filter_out + noise_of_filter_out;SNR_dB接收模块接收模块% FileName:Forjietiao 9.8K.m% clear;Fs=50000;% 读入信道输出信号数据recvsignal, Fs = wavread(Chanel_OUT.wav);t =

7、 (1/Fs:1/Fs:length(recvsignal)/Fs);% 本地载波频率fc_local1 = 10000 -200;% fc_local = 10000 -100;% fc_local = 10000;% 本地载波local_carrier1 = cos(2*pi*fc_local1.*t);% 相干解调xianggan_out1 = recvsignal.*local_carrier1;% 设计 3003400Hz 的带通滤波器fenzi, fenmu = butter(3, 300 3400/(Fs/2);demod_out1 = filter(fenzi, fenmu,

8、xianggan_out1);%sound(demod_out1/max(demod_out1), Fs);wavwrite(demod_out1, Fs, SSBDemod_OUT_9.8k.wav);figure(2);subplot(1, 2, 1); plot(5*demod_out1(53550:53750); axis(0 200 -0.3 0.3);title(解调信号波形);xlabel(时间（样值数）);subplot(1, 2, 2); psd(5*demod_out1, 10000, Fs); axis(0 2500 -20 10);title(解调信号功率谱);xlab

9、el(频率/Hz);ylabel(功率谱/(dB);接收模块接收模块%FileName:Forjietiao 9.9K.m%clear;Fs=50000;% 读入信道输出信号数据recvsignal, Fs = wavread(Chanel_OUT.wav);t = (1/Fs:1/Fs:length(recvsignal)/Fs);% 本地载波频率%fc_local = 10000 -200;fc_local2 = 10000 -100;%fc_local = 10000;% 本地载波local_carrier2 = cos(2*pi*fc_local2.*t);% 相干解调xianggan

10、_out2 = recvsignal.*local_carrier2;% 设计 3003400Hz 的带通滤波器fenzi, fenmu = butter(3, 300 3400/(Fs/2);demod_out2 = filter(fenzi, fenmu, xianggan_out2);%sound(demod_out2/max(demod_out2), Fs);wavwrite(demod_out2, Fs, SSBDemod_OUT_9.9k.wav);figure(3);subplot(1, 2, 1); plot(5*demod_out2(53550:53750); axis(0

11、200 -0.3 0.3);title(解调信号波形);xlabel(时间（样值数）);subplot(1, 2, 2); psd(5*demod_out2, 10000, Fs); axis(0 2500 -20 10);title(解调信号功率谱);xlabel(频率/Hz);ylabel(功率谱/(dB);接收模块接收模块%FileName:Forjietiao 10K.m%clear;Fs=50000;% 读入信道输出信号数据recvsignal, Fs = wavread(Chanel_OUT.wav);t = (1/Fs:1/Fs:length(recvsignal)/Fs);%

12、本地载波频率%fc_local = 10000 -200;%fc_local = 10000 -100;fc_local3 = 10000;% 本地载波local_carrier3 = cos(2*pi*fc_local3.*t);% 相干解调xianggan_out3 = recvsignal.*local_carrier3;% 设计 3003400Hz 的带通滤波器fenzi, fenmu = butter(3, 300 3400/(Fs/2);demod_out3 = filter(fenzi, fenmu, xianggan_out3);%sound(demod_out/max(dem

13、od_out), Fs);wavwrite(demod_out3, Fs, SSBDemod_OUT_10k.wav);figure(4);subplot(1, 2, 1); plot(5*demod_out3(53550:53750); axis(0 200 -0.3 0.3);title(解调信号波形);xlabel(时间（样值数）);subplot(1, 2, 2); psd(5*demod_out3, 10000, Fs); axis(0 2500 -20 10);title(解调信号功率谱);xlabel(频率/Hz);ylabel(功率谱/(dB);对比效果对比效果%filename:Forduibi.m%将原来信号的频谱和三次解调出来的频谱结果作对比，并分析结果figure(5);subplot(2, 2, 1); psd(wav, 10000, Fs); axis(0 2500 -20 10);title(基带信号功率谱);xlabel(频率/Hz);ylabel(功率谱/(dB);subplot(2, 2, 2); psd(5*demod_out1, 10000, Fs); axis(0 2500 -20 10);title(9.8KHz解调信号功率谱);xlabel(频率/Hz);ylabel(功率谱/(dB);subplot(2, 2, 3);