资源描述：
《空域相关滤波ssnf算法程序》由会员上传分享，免费在线阅读，更多相关内容在工程资料-天天文库。
1、%%%%%%%%%%%%%%%%%%%%%%%空域相关滤波％%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%参考文献：%Wavelettransformdomainfilters:aspatiallyselectivenoisefiltrationtechnique%不能选正交小波，文献中提出用二次样条小波(quadratic-spline).此处用双正交小波：bior1.5%优点：%1.对于信噪比高的信号滤波效果好；%2.对于边沿的保护强过阈值滤波，不会产生
2、阈值滤波情况下的过于平滑与Gibbs现象。%缺点：%1.由于对边沿信号没做任何处理，所以边沿可能会有脉冲噪声保留下来；%2.计算相关系数中，如杲计算出来的小波系数点位置偏差大，则相关系数计算受影响；%3.需要迭代运算，迭代的噪声能量阈值选取很重要，这里以开始段无信号处估计噪声；%4.需要迭代运算，所以运算量比阈值法大；%5.受分解层次影响，在大尺度上小波系数点位置偏差更大，相关系数计算不准确。%需要具体调整的地方：%1.分解的尺度；%2.选定用什么信号作为噪声的估计；%3.设定停止迭代的噪声能量阈值参数cc。%%%%%%%%%%%%%%%
3、%%%%%%%%空域相关滤波％%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%closeall;clc;clear;snr=5;init=2055615866;[xref,x]=wnoise(l,10,snr,init);signal=x;points=1024;level=5;wf=rbior1.5';%sym8,bior1.5%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
4、%%%%%%%%%%阈值消噪：S_thr=wden(signal,'rigrsure,,'s,,,mln',5,'sym8,);%%rigrsure;heursure;sqtwolog;minimaxi%%one;sln;mln%subplot(21l);plot(signal);%titleC阈值滤波);%subplot(212);plot(S_thr);%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%进行二进制小波变换(离散平稳小波
5、变换)，并给出各级波形:[Lo_D,Hi_D,Lo_R,Hi_R]=wfilters(wf);[swa.swd]=swt(signalJevel,Lo_D,Hi_D);%figure;%subplot(level；lJ);plot(real(signal));gridon;axistight;%fori=l:level%subplot(Ievel+1,2,2*(i)+1);%plot(swa(i,:));axistight;gridon;xlabel(rtimer);%ylabel(strcat(faum2str(i)));%subp
6、lot(level+1,2,2*(i)+2);%plot(swd(i,:));axistight;gridon;%ylabel(strcat('dum2str(i)));%end%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%小波系数的处理：Swd_n=swd;swd_org=swd;mask_n=zeros(size(Swd_n));%先把系数处理矩阵设置为全0。forj=1:(Ievel-l)%在l:(level-l)分解层次上
7、对高频系数处理，最后一层无法求相关系数，所以不作处理。Noise_d1=swd_org(j,:);Noise_d1=Noise_d1(1:80);Noise_var=var(Noise_dl);%以信号的前80个只含有噪声的点估计噪声在各层的方差。Pw_var=var(swd_org(j,:));Corr=swd_org(j,:.*swd_org(j+1,:%定义相关系数为相邻两层的乘积。cc=1.7;%用以设定停止迭代的噪声能量阈值，需要根据情况调节。%whilePw_var>cc*Noise_varPw=sum(abs(swd(j,:
8、)).A2);%计算小波能呈Pcorr=sum(abs(Corr).A2);%计算相关系数能量Corr_new=Corr.*((Pw/Pcorr)A0.5);%归一化corr_mod=abs(
