FFT_Filter.rar_FFT滤波_fft_filter_fftfilter_fiftyzbm_简谐波与FFT

%%%%%%%%%%%%load原始数据%%%%%%%%%%% clear all; close all load('D:\Program\Xiaozhou\Flat\20160408_10_incldpeakq.mat') Sensors20160408190205(:,20)=[];Sensors20160408190205(:,15)=[];Sensors20160408190205(:,15)=[]; Sensors20160408190531(:,20)=[];Sensors20160408190531(:,15)=[];Sensors20160408190531(:,15)=[]; Sensors20160408190921(:,20)=[];Sensors20160408190921(:,15)=[];Sensors20160408190921(:,15)=[]; Sensors20160408191341(:,20)=[];Sensors20160408191341(:,15)=[];Sensors20160408191341(:,15)=[]; Fs=5000; xt1=Sensors20160408190205(:,20); %%%%%%%%%%%%傅里叶变换%%%%%%%%%%% N=length(xt1); %数据长度 n=0:N-1; t1=n/Fs; %数据刻度 f=n*Fs/N; %频谱刻度 f0=Fs/N; %频率分辨率 xdft = fft(xt1); %傅里叶变换 xdft2 = xdft(1:length(xt1)/2+1); %频谱一半 xdft2 = 1/length(xt1).*xdft2; %归一化 xdft2(2:end-1) = 2*xdft2(2:end-1); %单边频谱 freq = 0:Fs/length(xt1):Fs/2; %单边频谱刻度 % figure (1) % plot(freq,abs(xdft2),'b'); % 10Hz对应855个点 % hold on %%%%%%%%%%%%设定截止频率--低通滤波%%%%%%%%%%% fstop=10; %设定截断频率 fspnumb=round(fstop/f0); xdft2(fspnumb:length(xdft2))=0; %plot(freq,abs(xdft2),'r'); % 10Hz对应855个点 %%%%%%%%%%%%逆傅里叶变换%%%%%%%%%%% xdft3=xdft2; back=ifft(xdft3); %逆傅里叶变换 error=xt1-back; %误差 figure (11) xstat=56.8; %显示开始时间段 xstop=xstat+0.5; %显示结束时间段 plot(t1,xt1,'b') hold on plot(t1,back,'r') xlim([xstat xstop]);grid on figure (12) plot(t1,error) xlim([xstat xstop]);grid on % xdft3(2:end-1)=xdft2(2:end-1)./2; % xdft3=xdft3.*length(xt1); % for j=length(xt1)/2+2:length(xt1) % xdft3(j)=conj(xdft3(length(xt1)-j+2)); % end % figure (6) % error2=xdft3-xdft; %原来的fft图与恢复后的fft图的误差 % subplot(4,1,1);plot(real(xdft));title('最初的fft图实部'); xlim([0,50]) % subplot(4,1,2);plot(real(xdft3));title('恢复后的fft图实部');xlim([0,50]) % subplot(4,1,3);plot(imag(xdft));title('最初的fft图虚部');xlim([0,50]) % subplot(4,1,4);plot(imag(xdft3));title('恢复后的fft图虚部');xlim([0,50])