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SecondOrderLowPass Struct Reference

Second order low pass filter structure. More...

#include <low_pass_filter.h>

Data Fields

float a [2]
 denominator gains More...
 
float b [2]
 numerator gains More...
 
float i [2]
 input history More...
 
float o [2]
 output history More...
 

Detailed Description

Second order low pass filter structure.

using biquad filter with bilinear z transform

http://en.wikipedia.org/wiki/Digital_biquad_filter http://www.earlevel.com/main/2003/03/02/the-bilinear-z-transform

Laplace continious form:

            1

H(s) = ----------------— s^2/w^2 + s/w*Q + 1

Polynomial discrete form:

   b0 + b1 z^-1 + b2 z^-2

H(z) = -------------------— a0 + a1 z^-1 + a2 z^-2

with: a0 = 1 a1 = 2*(K^2 - 1) / (K^2 + K/Q + 1) a2 = (K^2 - K/Q + 1) / (K^2 + K/Q + 1) b0 = K^2 / (K^2 + K/Q + 1) b1 = 2*b0 b2 = b0 K = tan(pi*Fc/Fs) ~ pi*Fc/Fs = Ts/(2*tau) Fc: cutting frequency Fs: sampling frequency Ts: sampling period tau: time constant

Definition at line 117 of file low_pass_filter.h.

Field Documentation

float SecondOrderLowPass::a[2]
float SecondOrderLowPass::b[2]
float SecondOrderLowPass::i[2]

input history

Definition at line 120 of file low_pass_filter.h.

Referenced by init_second_order_low_pass(), and update_second_order_low_pass().


The documentation for this struct was generated from the following file: