clf;clear; %设置初值 f0=50; Ts=0.001; fs=1/Ts; NLen=512; n=0:NLen-1; %陷波器的设计 apha=-2*cos(2*pi*f0*Ts); beta=0.96; b=[1 apha 1]; a=[1 apha*beta beta^2]; figure(1); freqz(b,a,NLen,fs);%陷波器特性显示 x=sin(2*pi*50*n*Ts)+sin(2*pi*125*n*Ts);%原信号 y=dlsim(b,a,x);%陷波器滤波处理 %对信号进行频域变换。 xfft=fft(x,NLen); xfft=xfft.*conj(xfft)/NLen; y1=fft(y,NLen); y2=y1.*conj(y1)/NLen; figure(2);%滤除前后的信号对比。 subplot(2,2,1);plot(n,x);grid; xlabel('Time (s)');ylabel('Amplitude');title('Input signal'); subplot(2,2,3);plot(n,y);grid; xlabel('Time (s)');ylabel('Amplitude');title('Filter output'); subplot(2,2,2);plot(n*fs/NLen,xfft);axis([0 fs/2 min(xfft) max(xfft)]);grid; xlabel('Frequency (Hz)');ylabel('Magnitude (dB)');title('Input signal'); subplot(2,2,4);plot(n*fs/NLen,y2);axis([0 fs/2 min(y2) max(y2)]);grid; xlabel (dB)');title('Filter output'); (Hz)');ylabel('Magnitude ('Frequency