SbComplexFIR

Overview

Sub-band Complex FIR Filter module

Discussion

Part of DSP Concepts IP for implementing long FIR filters in the frequency domain. This module implements a complex FIR filter within each subband of a filterbank. At instantiation time, you specify the number of taps in each complex filter The complex coefficients array (coeffs) will be sized as FFTSize * numTaps, so each bin has its own set of coefficients of length numTaps. The coeffs array requires all the real coefficients in the first half of the array, followed by the imaginary coefficients. The ordering of the coeff array is:

[realTap0Bin0, realTap0Bin1... realTap0BinM, realTap1Bin0, realTap1Bin1... realTapNBinM, imagTap0Bin0... imagTap0BinM, imagTap1Bin0... imagTapNBinM]

The module allocates memory for the complex FIR coefficients and state variables and at run-time implements the complex convolutions

Type Definition

typedef struct _ModuleSbComplexFIR
{
    ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
    INT32 numTaps;                                // Length of each complex FIR filter
    INT32 stateIndex;                             // Write index in to current complex state variables
    FLOAT32* state;                               // FIR filter state memory
    FLOAT32* coeffs;                              // FIR filter coeffs array
} ModuleSbComplexFIRClass;

Variables

Properties

Pins

Input Pins

Name: in

Description: complex input

Data type: float

Channel range: 1

Block size range: Unrestricted

Sample rate range: Unrestricted

Complex support: Complex

Output Pins

Name: out

Description: complex output

Data type: float

MATLAB Usage

File Name: sb_complex_fir_module.m

 M = sb_complex_fir_module(NAME, NUMTAPS, FFTSIZE)
 Creates a module which perform complex FIR filtering.  The module operates on 
 complex subband data.  Arguments:
    NAME - name of the module.
    NUMTAPS - Number of taps in each complex FIR filter.
    FFTSIZE - optional argument which sets the default size of the IO pins.
              By default, FFTSIZE = 256 and it will be overwritten in pre-build
              function.
 This module is part of DSPC IP for efficient fast convolution.