lpf.h File Reference

Low Pass Filter. More...

#include "math.h"

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Data Structures
struct	a_lpf
	instance structure for Low Pass Filter More...

Macros
#define	A_LPF_INIT(alpha)
#define	A_LPF_INIT2(fc, ts)
#define	A_LPF_GEN(fc, ts)

Typedefs
typedef struct a_lpf	a_lpf
	instance structure for Low Pass Filter
typedef struct a_lpf	a::lpf

Functions
double	a_lpf_gen (double fc, double ts)
	generate for Low Pass Filter
void	a_lpf_init (a_lpf *ctx, double alpha)
	initialize for Low Pass Filter
double	a_lpf_iter (a_lpf *ctx, double x)
	calculate for Low Pass Filter
void	a_lpf_zero (a_lpf *ctx)
	zeroing for Low Pass Filter

Detailed Description

Low Pass Filter.

low frequencies are passed, high frequencies are attenuated.

\[ RC\frac{\text{d}V_{\mathrm o}}{\text{dt}}+V_{\mathrm o}=V_{\mathrm i} \]

\[ RC\frac{V_{\mathrm o}(n)-V_{\mathrm o}(n-1)}{T_s}+V_{\mathrm o}(n)=V_{\mathrm i}(n) \]

\[ V_{\mathrm o}(n)=\frac{RC}{RC+T_s}V_{\mathrm o}(n-1)+\frac{T_s}{RC+T_s}V_{\mathrm i}(n) \]

\[ V_{\mathrm o}(n)=(1-\alpha)V_{\mathrm o}(n-1)+\alpha V_{\mathrm i}(n) \]

\[ \alpha=\frac{T_s}{RC+T_s}=\frac{T_s}{{\frac{1}{2\pi f_c}}+T_s} \]

https://en.wikipedia.org/wiki/Low-pass_filter