biz.source_code.dsp.filter

Class IirFilterDesignFisher

java.lang.Object

biz.source_code.dsp.filter.IirFilterDesignFisher

public class IirFilterDesignFisher
extends Object

Calculates the coefficients of an IIR filter.

This class is based on a Java port of C source code by Anthony J. Fisher.

Method Summary

Modifier and Type	Method and Description
static IirFilterCoefficients	design(FilterPassType filterPassType, FilterCharacteristicsType filterCharacteristicsType, int filterOrder, double ripple, double fcf1, double fcf2) Designs an IIR filter and returns the IIR filter coefficients.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

design

public static IirFilterCoefficients design(FilterPassType filterPassType,
                                           FilterCharacteristicsType filterCharacteristicsType,
                                           int filterOrder,
                                           double ripple,
                                           double fcf1,
                                           double fcf2)

Designs an IIR filter and returns the IIR filter coefficients.

The cutoff frequencies are specified relative to the sampling rate and must be between 0 and 0.5.
The following formula can be used to calculate the relative frequency values:

   frequencyInHz / samplingRateInHz

For Bessel filters, matched Z-transform is used to design the filter.

Parameters:

filterPassType - The filter pass type (Lowpass, highpass, bandpass, bandstop).

filterCharacteristicsType - The filter characteristics type. The following filters are implemented: Butterworth, Chebyshev (type 1), Bessel.

filterOrder - The filter order.

ripple - Passband ripple in dB. Must be negative. Only used for Chebyshev filter, ignored for other filters.

fcf1 - The relative filter cutoff frequency for lowpass/highpass, lower cutoff frequency for bandpass/bandstop. This value is relative to the sampling rate (see above for more details).

fcf2 - Ignored for lowpass/highpass, the relative upper cutoff frequency for bandpass/bandstop, This value is relative to the sampling rate (see above for more details).

Returns:

The IIR filter coefficients.