【信号传输】基于带通滤波器的信号传输（调制、解调、滤波）附Matlab代码.zip

clear all; close all; clc; load 'binome18.mat' load 'bp18.mat' Fs=100; M = 2^8; freq=linspace(0,1,M)*Fs; figure plot(freq,abs(fft(Strbbr,M))); xlabel 'Freqency(R)' title('原始信号'); zero=zeros(1000,1); Strbbr=[Strbbr;zero]; %we add some zeros in the signal to cancel the filter delay. %PART1:Interference Rejection carrierfrq= 9; signal18=filter(bp18,Strbbr); %the filter length is 464 signal18_=signal18(232:end);%remove the filter delay figure plot(freq,abs(fft(signal18_,M))); title('带阻滤波器信号'); %Part 2: Find back the baseband signal time=(-0.01:0.01:455.67); T1=cos(2*pi*carrierfrq*time); I1=signal18_.*T1.'; T2=-sin(2*pi*carrierfrq*time); Q1=signal18_.*T2.'; figure subplot(2,1,1); plot(freq,abs(fft(Q1,M))); title('滤波前I Part'); subplot(2,1,2); plot(freq,abs(fft(Q1,M))); title('滤波前Q Part'); load 'lowpass.mat' I2=filter(lowpass,I1); Q2=filter(lowpass,Q1); I3=I2(253:end); %remove the filter delay Q3=Q2(253:end); figure subplot(2,1,1); plot(freq,abs(fft(I3,M))); title('滤波后Q Part'); subplot(2,1,2); plot(I3); xlabel '0.01 Ts' title('滤波后Q Part'); figure subplot(2,1,1); plot(freq,abs(fft(Q3,M))); title('滤波后I Part'); subplot(2,1,2); plot(Q3); xlabel '0.01 Ts' title('滤波后I Part'); %Part 3:matched filter load 'Cercle.mat' %we guess the cercle filter is reshaping filter figure plot(h,'r') h=h(end:-1:1); I4 = conv(h,I3); Q4 = conv(h,Q3); %this the matched filter figure subplot(2,1,1); plot(freq,abs(fft(Q4,M))); title('I Part after using matched filter '); subplot(2,1,2); plot(Q4); title('I Part after using matched filter '); % sampling the signal and draw constellation ind = 100:100:448*100; xconst = (I4(ind) + 1i*Q4(ind)); figure plot(xconst, 'xg'); grid on %Part 4:Error Correcting Code for i = 1:length(ind) if I4(ind(i))<0 && I4(ind(i))>-1 && Q4(ind(i))>1 m(i,:)=[0;0;0]; elseif I4(ind(i))>1 && Q4(ind(i))>1 m(i,:)=[1;0;0]; elseif I4(ind(i))<-1 && Q4(ind(i))>0 m(i,:)=[0;0;1]; elseif I4(ind(i))>0 && I4(ind(i))<1 && Q4(ind(i))>0 m(i,:)=[0;1;0]; elseif I4(ind(i))>1 && Q4(ind(i))<0 m(i,:)=[1;1;0]; elseif I4(ind(i))<0 && I4(ind(i))>-1 && Q4(ind(i))<0 m(i,:)=[0;1;1]; elseif I4(ind(i))<-1 && Q4(ind(i))<-1 m(i,:)=[1;1;1]; elseif I4(ind(i))>0 && Q4(ind(i))<-1 m(i,:)=[1;0;1]; end end n = 6; k = 3; G = [1 0 0 0 1 0; 0 1 0 1 0 1 ; 0 0 1 1 1 1]; C=reshape(m,[1344/n,n]); % find H G1 = G(:,4:6); G3 = eye(3); H = [G1;G3]; H1 = H'; dec_info = 0:7; info_tab = de2bi(dec_info',3); coded_info_tab = mod(info_tab*G,2); Hamming_weight = sort(sum(coded_info_tab'),'ascend'); dmin = Hamming_weight(2); p=floor((dmin-1)/2); finil = C(:,1:3); data = reshape(finil',1,[])'; Result=bit2char(data)