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 4numChannelsnumStages 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: \([b0; b1; b2; a1; a2].\)

Module Pack

Standard

ClassID

classID = 132

Type Definition

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
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 
 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.