matlab中设计低通滤波器-飞外

可以通过Filter Builder交互界面设计，这里选择Lowpass。

指定参数，选择FIR滤波器，采样频率128Hz，通带截止频率15Hz，阻带截止频率16Hz。通带最大波纹0.1dB，阻带最小衰减60dB。这里选用Kaiser窗法设计（或等波纹法equiripple）。

可以生成对应的代码

function Hd = getFilter%GETFILTER Returns a discrete-time filter object.% MATLAB Code% Generated by MATLAB(R) 9.3 and DSP System Toolbox 9.5.% Generated on: 22-Jun-2020 15:08:24Fpass = 15; % Passband FrequencyFstop = 16; % Stopband FrequencyApass = 0.1; % Passband Ripple (dB)Astop = 60; % Stopband Attenuation (dB)Fs = 128; % Sampling Frequencyh = fdesign.lowpass('fp,fst,ap,ast', Fpass, Fstop, Apass, Astop, Fs);% 等波纹法%Hd = design(h, 'equiripple', 'MinOrder', 'any', 'StopbandShape', 'flat');% kaiser窗法Hd = design(h, 'kaiserwin');

查看滤波器特性

Hlp = getFilter;freqz(Hlp) % fvtool(lpFilt)

通过filtfilt获得零相位延迟的滤波

y = filtfilt(Hlp.Numerator, 1, x); % filtfilt(b, 1, x)

滤波结果

也可以直接通过fdesign和design设计，跟前面是等价的。

Fpass = 15; % Passband FrequencyFstop = 16; % Stopband FrequencyApass = 0.1; % Passband Ripple (dB)Astop = 60; % Stopband Attenuation (dB)Fs = 128; % Sampling Frequencyh = fdesign.lowpass('fp,fst,ap,ast', Fpass, Fstop, Apass, Astop, Fs);% 等波纹法%Hd = design(h, 'equiripple', 'MinOrder', 'any', 'StopbandShape', 'flat');% kaiser窗法Hd = design(h, 'kaiserwin');

也可以通过designfilt设计数字滤波器，结果是一样的。

lpFilt = designfilt('lowpassfir','PassbandFrequency',15/64, ... 'StopbandFrequency',16/64,'PassbandRipple',0.1, ... 'StopbandAttenuation',60,'DesignMethod','kaiserwin');y = filtfilt(lpFilt, x);

滤波结果