小波平移变量不变法的去噪

周文静

• %%%%%%转载自http://forum.vibunion.com/thread-9141-2-1.html
• clear;
• clc; %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
• %% 1.原始信号 f=50; % 信号频率
• fs=800; % 采样频率
• N=128; % 采样点 % 信号赋值
• n=1:N;
• y=sin(2*pi*f*n/fs); %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
• %% 2.噪声
• noise=0.4*rand(1,128); %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
• %% 3.染噪信号
• y_noise=y+noise; %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
• %% 4.硬消噪采用cycle_spinning技术 % 累加量
• z5=zeros(1,N); % 平移变换频移法
• for i=1:N;
• z=circshift(y_noise.',i-1).'; % 源信号右平移
• [z1,z2]=lwt(z,'db3'); % 小波正变换
• z2=zeros(1,N/2); % 高频分量全部为零（主要噪声，硬消噪）
• z3=ilwt(z1,z2,'db3'); % 小波反变换
• z4=circshift(z3.',-(i-1)).'; % 变换后信号左平移
• z5=z5+z4/N; % 平均
• end;
• %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
• %% 5.显示 error=norm(y-z5)/norm(y); % 相对误差 figure(1);
• subplot(2,1,1)
• plot(y,'r');
• legend('源信号');
• subplot(2,1,2);
• plot(y_noise);
• legend('染噪信号');
• figure(2);
• subplot(2,1,1)
• plot(y,'r');
• legend('源信号');
• title(error);
• subplot(2,1,2);
• plot(z5);
• legend('消噪后信号');