Overview

2nd order cascaded IIR filter, high precision

Discussion

Second order cascaded 5 multiply recursive filter with algorithm precision uses 24x24 with 56-bit accumulator. The module is designed to operate on multiple channels and applies the same coefficients across all channels. The state array is allocated to contain 6*numStages*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 module implements the difference equation:

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

Type Definition

typedef struct _ModuleBiquadCascadeHPFract32
{
    ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
    INT32 numStages;                              // Number of cascaded stages of the second order filter.
    INT32 bShift;                                 // Number of bits to shift of Numerator coefficients
    INT32 aShift;                                 // Number of bits to shift of Denominator coefficients
    FLOAT32* coeffs;                              // coefficients
    fract32* coeffsFract32;                       // coefficients in Fract32
    fract32* state;                               // State variables. 6 per channel.
} ModuleBiquadCascadeHPFract32Class;

Variables

Properties

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_cascadeHP_fract32_module.m

 M=biquad_cascadeHP_fract32_module(NAME, NUMSTAGES)
 Creates a second order IIR cascaded filter Fract32 (biquad) for use with the Audio
 Weaver.  Arguments:
     NAME - name of the module.
    NUMSTAGES - number of second order filter stages.