iirfilter: IIR filter init

Tools for initialising parameters for an IIR filter layer.

IIRFilterSpec

class hypercoil.init.iirfilter.IIRFilterSpec(Wn: float | Tuple[float, float], N: int, ftype: Literal['butter', 'cheby1', 'cheby2', 'ellip', 'bessel'] = 'butter', btype: Literal['bandpass', 'bandstop', 'lowpass', 'highpass'] = 'bandpass', fs: float | None = None, rp: float = 0.1, rs: float = 20, norm: Literal['phase', 'mag', 'delay'] = 'phase')

Specification for filter coefficients for recursive IIR filter classes.

Parameters:

Wnfloat or tuple(float, float)

Critical or cutoff frequency. If this is a band-pass filter, then this should be a tuple, with the first entry specifying the high-pass cutoff and the second entry specifying the low-pass frequency. This should be specified relative to the Nyquist frequency if fs is not provided, and should be in the same units as fs if it is provided.

Nint or Tensor (default 1)

Filter order.

ftypeone of ('butter', 'cheby1', 'cheby2', 'ellip', 'bessel', 'kuznetsov')

Filter class to initialise: Butterworth, Chebyshev I, Chebyshev II, elliptic, or Bessel-Thompson.

Note

To initialise an ideal filter, use a frequency product filter instead.

btype'bandpass' (default) or 'bandstop' or 'lowpass' or 'highpass'

Filter pass-band to emulate: low-pass, high-pass, or band-pass. The interpretation of the critical frequency changes depending on the filter type.

fsfloat or None (default None)

Sampling frequency.

rpfloat (default 0.1)

Pass-band ripple. Used only for Chebyshev I and elliptic filters.

rsfloat (default 20)

Stop-band ripple. Used only for Chebyshev II and elliptic filters.

norm'phase' or 'mag' or 'delay' (default 'phase')

Critical frequency normalisation. Consult the scipy.signal.bessel documentation for details.

Attributes:

fs

Methods

initialise_coefs

initialise_coefs()