BiquadCascadeFract32

Overview

Cascade of second order Biquad filters

Discussion

A cascade of second order 5 multiply recursive filters. The module is designed to operate on multiple channels and applies the same coefficients across all channels. The state array is allocated to contain 4*numChannels*numStages values. Each 2nd order section implements the difference equation:

$y[n]=b_0x[n]+b_1x[n-1]+b_2x[n-2]-a_1y[n-1]-a_2y[n-2].$

The filter coefficients stored in the matrix .coeffs. This matrix is of dimension 5 x numStages and each column of the matrix corresponds to an individual 2nd order Biquad stage. Within each column, the coefficients are ordered as: $[b0; b1; b2; a1; a2].$

Type Definition

CODE

typedef struct _ModuleBiquadCascadeFract32
{
    ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
    INT32 numStages;                              // Number of stages in the filter. The filter order = 2 * numStages
    FLOAT32* coeffs;                              // Matrix of filter coefficients. The size of the matrix is 5 x numStages. Each column contains the variables for a biquad arranged as [b0; b1; b2; a1; a2].
    fract32* coeffsFract32;                       // Matrix of filter coefficients. The size of the matrix is 5 x numStages. Each column contains the variables for a biquad arranged as [b0; b1; b2; a1; a2].
    fract32* state;                               // State variables. 4 per channel.
    INT32* postShift;                             // Number of bits to shift
} ModuleBiquadCascadeFract32Class;

Variables

Properties

Name	Type	Usage	isHidden	Default value	Range	Units
numStages	int	const	0	1	1:1:32
coeffs	float*	parameter	0	[5 x 1]	Unrestricted
coeffsFract32	fract32*	derived	1	[5 x 1]	Unrestricted
state	fract32*	state	1	[4 x 1]	Unrestricted
postShift	int*	derived	1	[1 x 1]	Unrestricted

Pins

Input Pins

Name: in

Description: audio input

Data type: fract32

Channel range: Unrestricted

Block size range: Unrestricted

Sample rate range: Unrestricted

Complex support: Real

Output Pins

Name: out

Description: audio output

Data type: fract32

MATLAB Usage

File Name: biquad_cascade_fract32_module.m

CODE

 M=biquad_cascade_fract32_module(NAME, NUMSTAGES)
 Creates a fract32 module that implements a cascade of second order Biquad
 stages.  This module can be used to implement high order IIR filters.
 The module operates on multiple channels and uses the same set of
 coefficients across channels.  Arguments:
    NAME - name of the module.
    NUMSTAGES - number of biquad stages.  The overall filter order
       is 2*NUMSTAGES.