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Dynamic runtime IIR Biquad filter coefficient generator (Q16.16 fixed-point).

  • #include "../common/syn_defs.h"
  • #include "../util/syn_qmath.h"
  • #include "syn_biquad.h"

Classes

Type Name
struct SYN_BiquadCoeffs
Normalized Biquad filter coefficients (where a0 = 1.0).

Public Functions

Type Name
SYN_Status syn_filter_design_apply_to_biquad (const SYN_BiquadCoeffs * coeffs, SYN_FilterBiquad * biquad)
Apply calculated coefficients to a SYN_FilterBiquad instance.
SYN_Status syn_filter_design_bandpass (q16_t fc_hz, q16_t fs_hz, q16_t Q, SYN_BiquadCoeffs * out)
Calculate Bandpass filter coefficients (constant skirt gain).
SYN_Status syn_filter_design_highpass (q16_t fc_hz, q16_t fs_hz, q16_t Q, SYN_BiquadCoeffs * out)
Calculate Butterworth Highpass filter coefficients.
SYN_Status syn_filter_design_lowpass (q16_t fc_hz, q16_t fs_hz, q16_t Q, SYN_BiquadCoeffs * out)
Calculate Butterworth Lowpass filter coefficients.
SYN_Status syn_filter_design_notch (q16_t fc_hz, q16_t fs_hz, q16_t Q, SYN_BiquadCoeffs * out)
Calculate Notch / Bandstop filter coefficients.

Public Functions Documentation

function syn_filter_design_apply_to_biquad

Apply calculated coefficients to a SYN_FilterBiquad instance. 

SYN_Status syn_filter_design_apply_to_biquad (
    const SYN_BiquadCoeffs * coeffs,
    SYN_FilterBiquad * biquad
)

Parameters:

  • coeffs Calculated biquad coefficients.
  • biquad Target biquad filter instance.

Returns:

SYN_OK on success, SYN_INVALID_PARAM if NULL.

function syn_filter_design_bandpass

Calculate Bandpass filter coefficients (constant skirt gain). 

SYN_Status syn_filter_design_bandpass (
    q16_t fc_hz,
    q16_t fs_hz,
    q16_t Q,
    SYN_BiquadCoeffs * out
)

Parameters:

  • fc_hz Center frequency in Hz (Q16.16).
  • fs_hz Sampling frequency in Hz (Q16.16).
  • Q Quality factor / bandwidth selectivity (Q16.16, e.g., Q16_FROM_FLOAT(2.0)).
  • out Pointer to output coefficient structure.

Returns:

SYN_OK on success, SYN_INVALID_PARAM if invalid.

function syn_filter_design_highpass

Calculate Butterworth Highpass filter coefficients. 

SYN_Status syn_filter_design_highpass (
    q16_t fc_hz,
    q16_t fs_hz,
    q16_t Q,
    SYN_BiquadCoeffs * out
)

Parameters:

  • fc_hz Cutoff frequency in Hz (Q16.16).
  • fs_hz Sampling frequency in Hz (Q16.16).
  • Q Quality factor (Q16.16, e.g., Q16_FROM_FLOAT(0.7071) for Butterworth).
  • out Pointer to output coefficient structure.

Returns:

SYN_OK on success, SYN_INVALID_PARAM if invalid.

function syn_filter_design_lowpass

Calculate Butterworth Lowpass filter coefficients. 

SYN_Status syn_filter_design_lowpass (
    q16_t fc_hz,
    q16_t fs_hz,
    q16_t Q,
    SYN_BiquadCoeffs * out
)

Parameters:

  • fc_hz Cutoff frequency in Hz (Q16.16).
  • fs_hz Sampling frequency in Hz (Q16.16).
  • Q Quality factor (Q16.16, e.g., Q16_FROM_FLOAT(0.7071) for Butterworth).
  • out Pointer to output coefficient structure.

Returns:

SYN_OK on success, SYN_INVALID_PARAM if invalid.

function syn_filter_design_notch

Calculate Notch / Bandstop filter coefficients. 

SYN_Status syn_filter_design_notch (
    q16_t fc_hz,
    q16_t fs_hz,
    q16_t Q,
    SYN_BiquadCoeffs * out
)

Parameters:

  • fc_hz Rejection frequency in Hz (Q16.16).
  • fs_hz Sampling frequency in Hz (Q16.16).
  • Q Quality factor / notch depth selectivity (Q16.16, e.g., Q16_FROM_FLOAT(5.0)).
  • out Pointer to output coefficient structure.

Returns:

SYN_OK on success, SYN_INVALID_PARAM if invalid.

The documentation for this class was generated from the following file src/syntropic/dsp/syn_filter_design.h