ButterBandpass

Description

Digital band-pass Butterworth IIR filter. Produces a 2N-order filter from the order-N analog prototype via the lp2bp transformation.

\[ \text{ButterBandpass}(N, W_{\text{low}}, W_{\text{high}}) \]

• order (int, \(\ge 1\)): order of the analog prototype. Effective digital order is 2 * order.

• low_cutoff, high_cutoff (floats in \((0, 1)\), with low < high): pass band as fractions of the Nyquist frequency.

Bit-exact match to scipy.signal.butter(order, [low, high], btype='bandpass') + scipy.signal.lfilter. Verified to ~1e-9 in tests/test_signal.py.

NaN handling

Policy: ignore. A NaN in any input at index t causes the function to skip that step: output at t is NaN and internal state is unchanged. Subsequent finite samples are processed as if step t had not occurred.

Examples

Description

from screamer import ButterBandpass
bp = ButterBandpass(order=4, low_cutoff=0.1, high_cutoff=0.3)
out = bp(signal)