org.knowceans.sandbox
Class FirFilter

java.lang.Object
  org.knowceans.sandbox.FirFilter

public class FirFilter
extends java.lang.Object

FirFilter implements a simple FIR filter, exploiting the symmetries of the complex spectrum of real signals.

Conventions: suffix z specifies a complex quantity or its size, they are stored with interleaved real and imaginary parts.

Author:

gregor heinrich

Constructor Summary

FirFilter()

Method Summary

static long	dualFir(double[] Wz, double[] Xz, double[] tempz, double[] Yz, double[] H1z, double[] H2z, int Nz) Frequency domain filtering of two real signals with two different real FIR filters.
static void	fft(double[] Xz, double[] Wz, int Nz) forward FFT
static void	fftr(double[] X, double[] Wz, int N) forward real-to-complex FFT with half length
static void	ffw(double[] Wz, int Nz) create FFT coefficients for size N
static long	fir(double[] Wz, double[] X, double[] tempz, double[] Y, double[] Hz, int N) Frequency domain filtering of one real sequence using half-size FFT.
static void	ifft(double[] Xz, double[] Wz, int Nz) inverse FFT
static void	ifftr(double[] Xz, double[] Wz, int Nz) inverse complex-to-real FFT with half length
static void	main(java.lang.String[] args)

Methods inherited from class java.lang.Object

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

Constructor Detail

FirFilter

public FirFilter()

Method Detail

ffw

public static void ffw(double[] Wz,
                       int Nz)

create FFT coefficients for size N

Parameters:

Wz - N/2 complex values

Nz - FFT size

fft

public static void fft(double[] Xz,
                       double[] Wz,
                       int Nz)

forward FFT

Parameters:

Xz - data (complex interleaved)

Wz - coefficients (complex interleaved)

Nz - FFT size (complex)

ifft

public static void ifft(double[] Xz,
                        double[] Wz,
                        int Nz)

inverse FFT

Parameters:

Xz - data (complex interleaved)

Wz - coefficients (complex interleaved)

Nz - FFT size (complex)

fftr

public static void fftr(double[] X,
                        double[] Wz,
                        int N)

forward real-to-complex FFT with half length

Parameters:

X - data [N] (real)

Yz - output [N/2 + 1] (complex)

Wz - [N/2] coefficients (complex interleaved, of full-size FFT)

N - FFT size (real)

ifftr

public static void ifftr(double[] Xz,
                         double[] Wz,
                         int Nz)

inverse complex-to-real FFT with half length

Parameters:

Xz - data (complex interleaved)

Wz - coefficients (complex interleaved)

Nz - FFT size (complex)

dualFir

public static long dualFir(double[] Wz,
                           double[] Xz,
                           double[] tempz,
                           double[] Yz,
                           double[] H1z,
                           double[] H2z,
                           int Nz)

Frequency domain filtering of two real signals with two different real FIR filters. Filtering of a complex signal is possible by using H1z == H2z.

Parameters:

Wz - [N/2] twiddling factors (complex interleaved)

Xz - [N] complex input vector (pair = real, imag) (complex interleaved)

tempz - [N] temporary buffer

Yz - [N] complex output vector (complex interleaved)

H1z - [N/2 + 1] DFT of IR for filter 1 (complex interleaved)

H2z - --"-- for filter 2 (complex interleaved)

Nz - length of input and output vectors (complex)

Returns:

fir

public static long fir(double[] Wz,
                       double[] X,
                       double[] tempz,
                       double[] Y,
                       double[] Hz,
                       int N)

Frequency domain filtering of one real sequence using half-size FFT.

Parameters:

Wz - [N/4] twiddling factors (complex interleaved, of half-size FFT)

Xz - [N] real input vector

tempz - [N] temporary buffer

Y - [N] real output vector

Hz - [N/4 + 1] DFT of IR (complex interleaved)

N - length of input and output vectors

Returns:

main

public static void main(java.lang.String[] args)