matlab_分数阶傅里叶变换对chirp信号进行解调，同时对比匹配滤波器的解调性能

clear all; close all; clc; N=1023; fi=0; f0=4000; %初始频率 fs=48e3; %抽样频率 k=2e5; %调频率 T=1/fs*N; B=k*T; f=zeros(1,N); t=zeros(1,N); global a; a=0.5; zero=zeros(N,1); %xunlian_data=[1,1,1]; shuju_data=randsrc(1,2000,[1,0;0.5,0.5]); %shuju_data=[1 0 0 1 1 1 0 0]; SNR=[-15:0]; %% 交织，加扰 M=size(shuju_data,2); s=2^(ceil(log2(M))); q=s/4-1; M=length(shuju_data); p=zeros(1,M); p(1)=0; for jj=2:M p(jj)=mod(21*p(jj-1)+q,s); while (p(jj)>=M) p(jj)=mod(21*p(jj)+q,s); end end data_interweave=zeros(1,M); for ii=1:M data_interweave(p(ii)+1)=shuju_data(ii); end figure; % plot(data_interweave,'*r-'); hold; plot(shuju_data,'k>-'); %% 调制 SS=length(shuju_data); fasong_data=[shuju_data]; hn=[1]; %figure;plot(hn); for n=-511:511 up_LFM1(n+512)=cos(2*pi*(f0-B)*n/fs+pi*k*((n/fs)*(n/fs))); %产生信号t=n/fs t(n+512)=n/fs; %时间 f(n+512)=n*fs/N; %频率 end % k=data; for n=-511:511 down_LFM1(n+512)=cos(2*pi*f0*n/fs-pi*k*((n/fs)*(n/fs))); %产生信号t=n/fs t(n+512)=n/fs; %时间 f(n+512)=n*fs/N; %频率 end for n=-511:511 up_LFM2(n+512)=cos(2*pi*f0*n/fs+pi*k*((n/fs)*(n/fs))); %产生信号t=n/fs t(n+512)=n/fs; %时间 f(n+512)=n*fs/N; %频率 end for n=-511:511 down_LFM2(n+512)=cos(2*pi*(f0+B)*n/fs-pi*k*((n/fs)*(n/fs))); %产生信号t=n/fs t(n+512)=n/fs; %时间 f(n+512)=n*fs/N; %频率 end len=length(shuju_data); data1=zeros(1,len/2); data2=zeros(1,len/2); data3=zeros(1,len/2); data4=zeros(1,len/2); j=1; for i=1:2:len if (shuju_data(1,i)==0)&(shuju_data(1,i+1)==0) data1(j)=1 else data1(j)=0 end j=j+1; end up_modulate1=data1'*up_LFM1; j=1; for i=1:2:len if (shuju_data(1,i)==0)&(shuju_data(1,i+1)==1) data2(j)=1 else data2(j)=0 end j=j+1; end down_modulate1=data2'*down_LFM1; j=1; for i=1:2:len if (shuju_data(1,i)==1)&(shuju_data(1,i+1)==0) data3(j)=1 else data3(j)=0 end j=j+1; end up_modulate2=data3'*up_LFM2; j=1; for i=1:2:len if (shuju_data(1,i)==1)&(shuju_data(1,i+1)==1) data4(j)=1 else data4(j)=0 end j=j+1; end down_modulate2=data4'*down_LFM2; modulate_matrix=up_modulate1+down_modulate1+up_modulate2+down_modulate2; modulate_signal=reshape(modulate_matrix',[],1); figure;plot((1:length(modulate_signal))./fs,modulate_signal); %wavwrite(modulate_signal,fs,'signal6.wav'); %% 解调 for iii=1:length(SNR) jieshou_data=awgn(modulate_signal,SNR(iii)); N_jietiao=N; r=0.002; a1=[0:r:2]; % f=(1:N_jietiao)*fs/N_jietiao; G1=zeros(length(a1),N_jietiao); h1=0; code_jietiao=[]; %解调出的编码 for kk=1:SS/2 h=0; n_start=(kk-1)*N_jietiao+1; n_end=kk*N_jietiao; X=jieshou_data(n_start:n_end); for l=1:length(a1) T1=frft(X,a1(l)); G1(l,:)=abs(T1(:)); u1(l)=-cot(a1(l)*pi/2)*fs/(t(N)-t(1)); if(h1<=max(abs(T1(:)))) h1=max(abs(T1(:))); p1=a1(l) %阶数 end end FF=frft(X,p1); [aa,bb]=max(abs(FF)); u0=f(bb); if(u0<0) p1=2-p1; end k tt=t(N)-t(1); %截取信号的持续时间 kk1=tt/(fs); kr=-cot(p1*pi/2)/kk1 %k参数估计式 %lg_r(i)=abs(log10(r1)); f0 ff0=u0*csc(p1*pi/2); %f0的估计值 if(ff0<2000&&ff0>-2000) code_jietiao=[code_jietiao,0,0]; elseif(ff0>2000&&ff0<6000) code_jietiao=[code_jietiao,1,0]; elseif(ff0<-2000&&ff0>-6000) code_jietiao=[code_jietiao,0,1]; elseif(ff0>6000) code_jietiao=[code_jietiao,1,1]; end end [number(iii),ratio(iii)]=biterr(shuju_data,code_jietiao); end save Mfsk_frft ratio