陷波器设计

2024-01-13 11:07:22

程序清单有

% 50Hz notch filter

% sample frequency=400

clear all;

clc;

b=[1 -sqrt(2) 1];

a=[1 -sqrt(2)*0.999 0.999];

[db, mag, pha, grd, w]=freqz_m(b, a);

subplot(221); plot(w*200/pi, db); title(' Magnitude Response' );

xlabel('frequency in Hz'); ylabel('dB'); axis([0, 100, -200, 5]);

set(gca, 'XTickMode', 'manual', 'XTick', [0, 50, 100]);

set(gca, 'YTickmode', 'manual', 'YTick', [-200, -100, 0]); grid

title('Notch filter response');

t0=1:8000;

t=1:256;

t1=1:100;

t2=1:128;

x=sin(2*pi*50*t0/400)+0.5*sin(2*pi*100*t0/400);

x1=x(t);

y=filter(b,a,x1);

subplot(222); plot(x1);

title('Original waveform');

X=fft(x1);

subplot(223); plot(t2*400/256,abs(X(t2)));

xlabel('frequency in Hz'); ylabel('|H|'); axis([0, 200, 0, 150]);

title('Spectrum for original');

set(gca, 'XTickMode', 'manual', 'XTick', [0, 50, 100, 150]);

set(gca, 'YTickmode', 'manual', 'YTick', [50, 100]); grid

y=filter(b,a,x);

x1=y(t+7600);

X=fft(x1);

subplot(224); plot(t2*400/256,abs(X(t2)));

xlabel('frequency in Hz'); ylabel('|H|'); axis([0, 200, 0, 150]);

title('Spectrum after filter');

set(gca, 'XTickMode', 'manual', 'XTick', [0, 50, 100, 150]);

set(gca, 'YTickmode', 'manual', 'YTick', [50, 100]); grid

figure(2);

subplot(611);plot(x(t1)); axis([1, 100, -1.5, 1.5]); ylabel('input x');

set(gca, 'YTickmode', 'manual', 'YTick', [-1,-0.5,0, 0.5,1]); grid

subplot(612);plot(y); axis([1, 100, -1.5, 1.5]); ylabel('first');

set(gca, 'YTickmode', 'manual', 'YTick', [-1,-0.5,0,0.5,1]); grid

subplot(613);plot(y); axis([401, 500, -1.5, 1.5]); ylabel('second');

set(gca, 'YTickmode', 'manual', 'YTick', [-1,-0.5,0, 0.5,1]); grid

subplot(614);plot(y); axis([1201, 1300, -1.0, 1.0]); ylabel('forth');