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/**
* \file miscFilter.h
* \brief Miscellaneous FIR/IIR filter design functions.
* \note Includes raw filters (filters without a design, except \f$f_{Sample}\f$).
* \copyright Copyright (C) 2006-2022 Ralf Hoppe <ralf.hoppe@dfcgen.de>
*/
#ifndef MISC_FILTER_H
#define MISC_FILTER_H
/* INCLUDE FILES **************************************************************/
#include "dfcgen.h" /* includes config.h (include before GNU system headers) */
#ifdef __cplusplus
extern "C" {
#endif
/* GLOBAL TYPE DECLARATIONS ***************************************************/
/** Miscellaneous filters.
*
* \attention Don't change the enums, because order must match list element
* index in dialog.
*/
typedef enum
{
MISCFLT_UNKNOWN = -1, /**< Unknown filter (no design data, raw filter) */
MISCFLT_HILBERT = 0, /**< Hilbert transformer (\e Fourier series expansion) */
MISCFLT_INT = 1, /**< Integrator (\e Fourier series expansion) */
MISCFLT_DIFF = 2, /**< Differentiator (\e Fourier series expansion)*/
MISCFLT_COMB = 3, /**< Comb filter */
MISCFLT_AVGFIR = 4, /**< Moving average filter (non-recursive type) */
MISCFLT_AVGIIR = 5, /**< Moving average filter (recursive type) */
MISCFLT_AVGEXP = 6, /**< Exponential average filter (1st order lowpass) */
MISCFLT_SIZE /**< Size of MISCFLT enum */
} MISCFLT;
/** Misc filter design constraints.
* \see DESIGNDLG_COMMON
*/
typedef struct
{
MISCFLT type; /**< Type of filter. \attention Must be the 1st element */
int order; /**< Order of filter. \attention Must be the 2nd element */
} MISCFLT_DESIGN;
/* GLOBAL CONSTANT DECLARATIONS ***********************************************/
/* GLOBAL VARIABLE DECLARATIONS ***********************************************/
/* GLOBAL MACRO DEFINITIONS ***************************************************/
/* EXPORTED FUNCTIONS *********************************************************/
/* FUNCTION *******************************************************************/
/** Generates a miscellaneous FIR/IIR filter. The following digital filters are
* supported:
* - \e Hilbert transformer (linear FIR): \f$\displaystyle{c_{n/2\pm k}=-\frac{2}{k\pi}}\f$ for odd k, else 0
* - Perfect integrator (FIR): \f$\displaystyle{c_{n/2\pm k}=\frac{1}{2}-\frac{1}{\pi}\Si(k\pi)}\f$
* - Perfect differentiator (linear FIR): \f$\displaystyle{c_{n/2\pm k}=\frac{(-1)^{k+1}}{k\pi}}\f$
* - Moving average (FIR): \f$H(z)=1+z^{-1}+z^{-2}+\cdots+z^{-n}\f$
* - Moving average (IIR): \f$\displaystyle{H(z)=\frac{1-z^{-n}}{1-z^{-1}}}\f$
* - Comb filter (FIR): \f$H(z)=1-z^{-n}\f$
* - Exponential average (IIR): \f$\displaystyle{H(z)=\frac{1}{n-(n-1)z^{-1}}}\f$
*
* \param pDesign Pointer to misc filter design data.
* \param pFilter Pointer to buffer which gets the generated filter.
* Notice, that memory space for polynomials will be
* allocated.
*
* \return - 0 (or GSL_SUCCESS) if okay and nothing has changed.
* - a negative number (typically GSL_CONTINUE) if a
* coefficient or the degree has changed, but the filter
* is valid. You can use the FLTERR_WARNING macro from
* filterSupport.h to check this condition.
* - a positive error number (typically from from errno.h
* or gsl_errno.h) that something is wrong and the
* filter must be seen as invalid. You can use the
* FLTERR_CRITICAL macro from filterSupport.h to check
* this condition.
******************************************************************************/
int miscFilterGen (const MISCFLT_DESIGN *pDesign, FLTCOEFF *pFilter);
#ifdef __cplusplus
}
#endif
#endif /* MISC_FILTER_H */
/******************************************************************************/
/* END OF FILE */
/******************************************************************************/
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