Filters a set of data with a digital Butterworth filter.

Syntax

OutSignal = ButterFilter(Order,Fc,InSignal)

OutSignal = ButterFilter(Order,Fc,Band,InSignal)

OutSignal = ButterFilter(Order,Fc1,Fc2,InSignal)

Arguments

Name

Description

Order

A positive integer specifying the order of the filter. For band pass and band stop filter, the order is twice this value.

Fc

The corner frequency in Hz of a low pass or high pass filter, or a vector of two corner frequencies for a band pass or band stop filter. For a digital filter Fc is normalized by the Nyquist frequency and has values in the interval (0,1). For an analog filter, Fc has positive value(s).

Band

(optional)

The filter band specifier. When Fc is a value, Band can be either ‘low’ (default) or ‘high.’ When Fc is a vector, Band is omitted for a band pass filter and ‘stop’ for a band stop filter.

Fc1, Fc2

For the Templex™ style convention, Fc1 and Fc2 are the normalized corner frequencies in Hz of a digital filter. For a low pass filter, Fc1 = 0. For a high pass filter, Fc2 = 0 or 1. For a band pass filter, Fc1 < Fc2. For a band stop filter, Fc1 > Fc2.

InSignal

A vector of real data to be filtered.

Output

Name

Description

OutSignal

A vector of filtered data. Same size as the input data.

Example

Filter a vector of data with a low-pass second order Butterworth filter with a corner frequency at 250 Hz, where the data sampling frequency is 1000 Hz.

Syntax

OutData = ButterFilter(2,0,250/500,InData)

Result

OutData is a vector of filtered data.

See Also:

Cheby1Filter

Cheby2Filter

EllipFilter