obspy.signal.filter.lowpass_cheby_2

lowpass_cheby_2(data, freq, df, maxorder=12, ba=False, freq_passband=False)[source]

Cheby2-Lowpass Filter

Filter data by passing data only below a certain frequency. The main purpose of this cheby2 filter is downsampling. #318 shows some plots of this filter design itself.

This method will iteratively design a filter, whose pass band frequency is determined dynamically, such that the values above the stop band frequency are lower than -96dB.

Parameters:

  • data (numpy.ndarray) – Data to filter.

  • freq – The frequency above which signals are attenuated with 95 dB

  • df – Sampling rate in Hz.

  • maxorder – Maximal order of the designed cheby2 filter

  • ba – If True return only the filter coefficients (b, a) instead of filtering

  • freq_passband – If True return additionally to the filtered data, the iteratively determined pass band frequency

Returns:

Filtered data.