Biquad

Overview

2nd order IIR filter

Discussion

Standard second order 5 multiply recursive filter. The module is designed to operate on multiple channels and applies the same coefficients across all channels. The state array is allocated to contain 2*numChannels values. The frequency response of the module is determined by the values of the 5 coefficients, and the coefficients come directly from the MATLAB second order representation. The leading a0 coefficient is not supplied and is assumed to equal 1.0. The order of the coefficients must be [b0 b1 b2 a1 a2]. The module implements the difference equation: \(y[n]=b_0x[n]+b_1x[n-1]+b_2x[n-2]-a_1y[n-1]-a_2y[n-2].\)

Module Pack

Standard

ClassID

classID = 10

Type Definition

typedef struct _ModuleBiquad
{
ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
FLOAT32 b0;                                   // First numerator coefficient.
FLOAT32 b1;                                   // Second numerator coefficient.
FLOAT32 b2;                                   // Third numerator coefficient.
FLOAT32 a1;                                   // Second denominator coefficient.
FLOAT32 a2;                                   // Third denominator coefficient.
FLOAT32* state;                               // State variables. 2 per channel.
} ModuleBiquadClass;

Variables

Properties

Name	Type	Usage	isHidden	Default Value	Range
b0	float	parameter	0	1	Unrestricted
b1	float	parameter	0	0	Unrestricted
b2	float	parameter	0	0	Unrestricted
a1	float	parameter	0	0	Unrestricted
a2	float	parameter	0	0	Unrestricted
state	float*	state	1	[2 x 1]	Unrestricted

Pins

Input Pins


Name	in
Description	audio input
Data type	float
Channel range	Unrestricted
Block size range	Unrestricted
Sample rate range	Unrestricted
Complex support	Real

Output Pins


Name	out
Description	audio output
Data Type	float

Matlab Usage

File Name: biquad_module.m 
 M=biquad_module(NAME) 
 Creates a second order IIR filter (biquad) for use with Audio 
 Weaver. 

 Arguments: 
     NAME - name of the module.