Filter Designer

Helps determining the order of digital filters

Helps determining the order of digital filters. Change the filter order to get suitable response. Supports butterworth and filtfilt filters.

function FilterDesigner(fc1,fc2,fs,type,orderh,orderl)

Input:

fc1: lower-bound cutoff frequency

fc2: upper-bound cutoff frequency

fs: sampling frequency

type: filter type 'butter' for butterworth, 'filtfilt' for filtfilt

orderh: filter order for high pass filter

orderl: filter order for low pass filter

Output:

Plots frequency response of the high-pass, low-pass, and band-pass filters.

Important Notes:

1-filtfilt filter here is assumed to be buttworth filter applied to the input data in both the forward and reverse directions to get rid of phase distortion.

2-After choosing the suitable filter order, apply the filter to your data using the following lines:

for butterworth:

[B1,A1] = butter(orderh,fc1/(fs/2),'high');
[B2,A2] = butter(orderl,fc2/(fs/2),'low');
yh=filter(B1,A1,x); %apply high-pass filter to the data
yl=filter(B2,A2,x); %apply low-pass filter to the data
y=filter(B2,A2,yh); %apply band-pass filter to the data

for filtfilt:

[B1,A1] = butter(orderh,fc1/(fs/2),'high');
[B2,A2] = butter(orderl,fc2/(fs/2),'low');
yh=filtfilt(B1,A1,x); %apply high-pass filter to the data
yl=filtfilt(B2,A2,x); %apply low-pass filter to the data
y=filtfilt(B2,A2,yh); %apply band-pass filter to the data

where

x: is the data vector.