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(8.D.2.5) 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

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

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.

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