Low Pass Filter

Collaboration diagram for Low Pass Filter:

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

Macros
#define	A_LPF_1(alpha)
#define	A_LPF_2(fc, ts)
#define	A_LPF_GEN(fc, ts)

Typedefs
typedef struct a_lpf	a_lpf
	instance structure for Low Pass Filter

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

Detailed Description

Macro Definition Documentation

A_LPF_1

#define A_LPF_1

(

alpha

)

Value:

{a_float_c(alpha), 0}

A_LPF_2

#define A_LPF_2	(		fc,
			ts )

Value:

{A_LPF_GEN(fc, ts), 0}

A_LPF_GEN

#define A_LPF_GEN	(		fc,
			ts )

Value:

(a_float_c(ts) / (A_FLOAT_1_TAU / a_float_c(fc) + a_float_c(ts)))

Function Documentation

a_lpf_gen()

a_float a_lpf_gen	(	a_float	fc,
		a_float	ts )

generate for Low Pass Filter

\begin{cases} \alpha=\frac{T_s}{RC+T_s},&\alpha\in[0,1]\\ RC=\frac{1}{2\pi f_c}. \end{cases}

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

Parameters

[in]	fc	cut-off frequency unit(hz)
[in]	ts	sampling time unit(s)

Returns

filter coefficient [0,1]

a_lpf_init()

void a_lpf_init	(	a_lpf *	ctx,
		a_float	alpha )

initialize for Low Pass Filter

Parameters

[in,out]	ctx	points to an instance of Low Pass Filter
[in]	alpha	filter coefficient [0,1]

a_lpf_iter()

a_float a_lpf_iter	(	a_lpf *	ctx,
		a_float	x )

calculate for Low Pass Filter

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

Parameters

[in,out]	ctx	points to an instance of Low Pass Filter
[in]	x	input value

Returns

output value

a_lpf_zero()

void a_lpf_zero

(

a_lpf *

ctx

)

zeroing for Low Pass Filter

Parameters

[in,out]

ctx

points to an instance of Low Pass Filter