滤波器设计库
此示例说明如何使用 Signal Processing Toolbox® 产品中的 designfilt
函数设计各种 FIR 和 IIR 数字滤波器。
该库旨在帮助您识别感兴趣的滤波器响应,查看代码,并在您自己的工程中使用它。它包含 designfilt
提供的每个可用滤波器响应的示例。但请注意,这些只是为每种响应类型设计滤波器的几种可能方式。有关设定集的详尽列表,请参阅 Signal Processing Toolbox 文档。
除非另有说明,否则在此示例中,所有频率均以赫兹为单位,所有波纹和衰减值均以分贝为单位。
低通 FIR 滤波器
等波纹设计
Fpass = 100; Fstop = 150; Apass = 1; Astop = 65; Fs = 1e3; d = designfilt('lowpassfir', ... 'PassbandFrequency',Fpass,'StopbandFrequency',Fstop, ... 'PassbandRipple',Apass,'StopbandAttenuation',Astop, ... 'DesignMethod','equiripple','SampleRate',Fs); fvtool(d)
低通 IIR 滤波器
最平坦设计
Fpass = 100; Fstop = 150; Apass = 0.5; Astop = 65; Fs = 1e3; d = designfilt('lowpassiir', ... 'PassbandFrequency',Fpass,'StopbandFrequency',Fstop, ... 'PassbandRipple',Apass,'StopbandAttenuation',Astop, ... 'DesignMethod','butter','SampleRate',Fs); fvtool(d)
通带和阻带中的波纹
N = 8; Fpass = 100; Apass = 0.5; Astop = 65; Fs = 1e3; d = designfilt('lowpassiir', ... 'FilterOrder',N, ... 'PassbandFrequency',Fpass, ... 'PassbandRipple',Apass,'StopbandAttenuation',Astop, ... 'SampleRate',Fs); fvtool(d)
高通 FIR 滤波器
等波纹设计
Fstop = 350; Fpass = 400; Astop = 65; Apass = 0.5; Fs = 1e3; d = designfilt('highpassfir','StopbandFrequency',Fstop, ... 'PassbandFrequency',Fpass,'StopbandAttenuation',Astop, ... 'PassbandRipple',Apass,'SampleRate',Fs,'DesignMethod','equiripple'); fvtool(d)
高通 IIR 滤波器
最平坦设计
Fstop = 350; Fpass = 400; Astop = 65; Apass = 0.5; Fs = 1e3; d = designfilt('highpassiir','StopbandFrequency',Fstop ,... 'PassbandFrequency',Fpass,'StopbandAttenuation',Astop, ... 'PassbandRipple',Apass,'SampleRate',Fs,'DesignMethod','butter'); fvtool(d)
通带和阻带中的波纹
N = 8; Fpass = 400; Astop = 65; Apass = 0.5; Fs = 1e3; d = designfilt('highpassiir', ... 'FilterOrder',N, ... 'PassbandFrequency',Fpass, ... 'StopbandAttenuation',Astop,'PassbandRipple',Apass, ... 'SampleRate',Fs); fvtool(d)
带通 FIR 滤波器
等波纹设计
Fstop1 = 150; Fpass1 = 200; Fpass2 = 300; Fstop2 = 350; Astop1 = 65; Apass = 0.5; Astop2 = 65; Fs = 1e3; d = designfilt('bandpassfir', ... 'StopbandFrequency1',Fstop1,'PassbandFrequency1', Fpass1, ... 'PassbandFrequency2',Fpass2,'StopbandFrequency2', Fstop2, ... 'StopbandAttenuation1',Astop1,'PassbandRipple', Apass, ... 'StopbandAttenuation2',Astop2, ... 'DesignMethod','equiripple','SampleRate',Fs); fvtool(d)
不对称频带衰减
N = 50; Fstop1 = 150; Fpass1 = 200; Fpass2 = 300; Fstop2 = 350; Wstop1 = 3; Wstop2 = 100; Fs = 1e3; d = designfilt('bandpassfir', ... 'FilterOrder',N, ... 'StopbandFrequency1',Fstop1,'PassbandFrequency1', Fpass1, ... 'PassbandFrequency2',Fpass2,'StopbandFrequency2', Fstop2, ... 'StopbandWeight1',Wstop1,'StopbandWeight2',Wstop2, ... 'DesignMethod','equiripple','SampleRate',Fs); fvtool(d)
带通 IIR 滤波器
最平坦设计
Fstop1 = 150; Fpass1 = 200; Fpass2 = 300; Fstop2 = 350; Astop1 = 65; Apass = 0.5; Astop2 = 65; Fs = 1e3; d = designfilt('bandpassiir', ... 'StopbandFrequency1',Fstop1,'PassbandFrequency1', Fpass1, ... 'PassbandFrequency2',Fpass2,'StopbandFrequency2', Fstop2, ... 'StopbandAttenuation1',Astop1,'PassbandRipple', Apass, ... 'StopbandAttenuation2',Astop2, ... 'DesignMethod','butter','SampleRate', Fs); fvtool(d)
通带和阻带中的波纹
N = 8; Fpass1 = 200; Fpass2 = 300; Astop1 = 65; Apass = 0.5; Astop2 = 65; Fs = 1e3; d = designfilt('bandpassiir', ... 'FilterOrder',N, ... 'PassbandFrequency1', Fpass1,'PassbandFrequency2', Fpass2, ... 'StopbandAttenuation1', Astop1, 'PassbandRipple', Apass, ... 'StopbandAttenuation2', Astop2, ... 'SampleRate', Fs); fvtool(d)
带阻 FIR 滤波器
等波纹设计
Fpass1 = 100; Fstop1 = 150; Fstop2 = 350; Fpass2 = 400; Apass1 = 0.5; Astop = 65; Apass2 = 0.5; Fs = 1e3; d = designfilt('bandstopfir', ... 'PassbandFrequency1',Fpass1,'StopbandFrequency1',Fstop1, ... 'StopbandFrequency2',Fstop2,'PassbandFrequency2',Fpass2, ... 'PassbandRipple1',Apass1,'StopbandAttenuation',Astop, ... 'PassbandRipple2', Apass2, ... 'DesignMethod','equiripple','SampleRate', Fs); fvtool(d)
不对称通带波纹
N = 30; Fpass1 = 100; Fstop1 = 150; Fstop2 = 350; Fpass2 = 400; Wpass1 = 1; Wpass2 = 10; Fs = 1e3; d = designfilt('bandstopfir', ... 'FilterOrder',N, ... 'PassbandFrequency1',Fpass1,'StopbandFrequency1',Fstop1, ... 'StopbandFrequency2',Fstop2,'PassbandFrequency2',Fpass2, ... 'PassbandWeight1',Wpass1,'PassbandWeight2',Wpass2, ... 'DesignMethod','equiripple','SampleRate', Fs); fvtool(d)
带阻 IIR 滤波器
最平坦设计
Fpass1 = 100; Fstop1 = 150; Fstop2 = 350; Fpass2 = 400; Apass1 = 0.5; Astop = 65; Apass2 = 0.5; Fs = 1e3; d = designfilt('bandstopiir', ... 'PassbandFrequency1',Fpass1,'StopbandFrequency1',Fstop1, ... 'StopbandFrequency2',Fstop2,'PassbandFrequency2',Fpass2, ... 'PassbandRipple1',Apass1,'StopbandAttenuation',Astop, ... 'PassbandRipple2', Apass2, ... 'DesignMethod','butter','SampleRate', Fs); fvtool(d)
通带和阻带中的波纹
N = 8; Fpass1 = 125; Fpass2 = 375; Apass = 0.5; Astop = 65; Fs = 1e3; d = designfilt('bandstopiir', ... 'FilterOrder',N, ... 'PassbandFrequency1',Fpass1,'PassbandFrequency2',Fpass2, ... 'PassbandRipple',Apass,'StopbandAttenuation', Astop, ... 'SampleRate',Fs); fvtool(d)
任意幅值 FIR 滤波器
单频带任意幅值设计
N = 300; % Frequencies are in normalized units F1 = 0:0.01:0.18; F2 = [.2 .38 .4 .55 .562 .585 .6 .78]; F3 = 0.79:0.01:1; FreqVect = [F1 F2 F3]; % vector of frequencies % Define desired response using linear units A1 = .5+sin(2*pi*7.5*F1)/4; % Sinusoidal section A2 = [.5 2.3 1 1 -.2 -.2 1 1]; % Piecewise linear section A3 = .2+18*(1-F3).^2; % Quadratic section AmpVect = [A1 A2 A3]; d = designfilt('arbmagfir',... 'FilterOrder',N,'Amplitudes',AmpVect,'Frequencies',FreqVect,... 'DesignMethod','freqsamp'); fvtool(d,'MagnitudeDisplay','Zero-phase')
多频带低通设计,阻带具有阶梯式衰减电平
N = 150; B = 2; % Number of bands % Frequencies are in normalized units F1 = [0 .25]; % Passband F2 = [.3 .4 .401 .5 .501 .6 .601 .7 .701 .8 .801 .9 .901 1]; % Stopband A1 = ones(size(F1)); % Desired amplitudes for band 1 in linear units A2 = zeros(size(F2)); % Desired amplitudes for band 2 in linear units % Vector of weights W = 10.^([0 0 5 5 10 10 15 15 20 20 25 25 30 30 35 35]/20); W1 = W(1:2); % Weights for band 1 W2 = W(3:end); % Weights for band 2 d = designfilt('arbmagfir', ... 'FilterOrder',N,'NumBands',B, ... 'BandFrequencies1',F1,'BandAmplitudes1',A1, ... 'BandFrequencies2',F2,'BandAmplitudes2',A2, ... 'BandWeights1',W1,'BandWeights2', W2); fvtool(d)
FIR 微分滤波器
全频带设计
N = 41; Fs = 1e3; d = designfilt('differentiatorfir', ... 'FilterOrder',N, 'DesignMethod','equiripple','SampleRate',Fs); fvtool(d,'MagnitudeDisplay','zero-phase','OverlayedAnalysis','phase')
部分频带设计
N = 40; Fpass = 100; Fstop = 150; Fs = 1e3; d = designfilt('differentiatorfir', ... 'FilterOrder',N, ... 'PassbandFrequency',Fpass,'StopbandFrequency',Fstop, ... 'DesignMethod','equiripple','SampleRate',Fs); fvtool(d,'MagnitudeDisplay','zero-phase','OverlayedAnalysis','phase')
希尔伯特 FIR 滤波器
等波纹设计
N = 40; Tw = 50; Fs = 1e3; d = designfilt('hilbertfir', ... 'FilterOrder',N,'TransitionWidth',Tw, ... 'DesignMethod','equiripple','SampleRate',Fs); fvtool(d,'MagnitudeDisplay','Zero-phase','OverlayedAnalysis','phase')