AN3984 datasheet(27/46 Pages) STMICROELECTRONICS

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AN3984

Matlab code (functions)

Doc ID 022240 Rev 1

27/46

A.3

Low-pass and high-pass filter (LHPassFilterAPW.m)

%-------------------------------------------------------------------------%

function [Coeff_Hex, CoeffAPW] = LHPassFilterAPW(CutOff_Freq, Q,

FType, Order, CoeffRange, Fc)

Args:Fc -> Cutoff Frequency

Q -> Quality factor

FType -> 0->LowPassFilter; 1->HighPass Filter

Order -> 1=1st order; 2=2nd order

CoeffRange -> Coefficient Range (1, 2 or 4)

Fc -> Sample frequency

Return: Coeff_Hex -> APW filter Coeff

- Hex

CoeffAPW -> APW filter Coeff

- Floating point

LimitVal -> Limit coeff value

Description: Generates the APWorkbench coeff for a LHPassFilter

STMicroelectronics - Agrate (ITALY)

MSH - Audio & Sound BU

Revision: 1.1

Date: 23 June 2011

%-------------------------------------------------------------------------%

%% Function code

function [Coeff_Hex, CoeffAPW, LimitValue] = LHPassFilterAPW(Fc, Q, ...

FType, Order, CoeffRange, Fs)

format long

if (nargin <6)

Fs = 96000;

end

Teta = (2*pi*Fc)/Fs;

%Angle from frequency

K = tan(Teta/2);

alpha = 1+K;

a2 = 0;

b2 = 0;

a0 = 1.0;

a1 = -(1-K)/alpha;

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