filtering#

Functions for filtering signal objects

Filter functions for matched filtering, pulse-shaping and impairment simulation.

qampy.filtering.filter_signal(signal, cutoff, ftype='bessel', order=2, analog=False)#

Apply a filter to a signal for simulating e.g. electrical bandwidth limitation

Parameters:

  • signal (SignalObject) – input signal

  • cutoff (float) – 3 dB cutoff frequency of the filter

  • ftype (string, optional) – filter type can be either a bessel, butter, exp or gauss filter (default=bessel)

  • order (int, optional) – order of the filter (default = 2)

  • analog (bool, optional) – whether to use analog filtering with lsim, much slower, but could give sligthly more accurate results for bessel and butter filters does not have an effect for other filters (default=False)

Returns:

signalout – filtered output signal

Return type:

SignalObject

qampy.filtering.filter_signal_analog(signal, cutoff, ftype='bessel', order=2)#

Legacy function will be deprecated Apply an analog filter to a signal for simulating e.g. electrical bandwidth limitation

Parameters:

  • signal (SignalObject) – input signal

  • cutoff (float) – 3 dB cutoff frequency of the filter

  • ftype (string, optional) – filter type can be either a bessel, butter, exp or gauss filter (default=bessel)

  • order (int, optional) – order of the filter (default = 2)

Returns:

signalout – filtered output signal

Return type:

SignalObject

qampy.filtering.pre_filter(signal, bw)#

Low-pass pre-filter signal with square shape filter

Parameters:

  • signal (SignalObject) – single polarization signal

  • bw (float) – bandwidth of the rejected part, given as fraction of overall length

Returns:

signal_out – filtered signal

Return type:

SignalObject

qampy.filtering.rrcos_pulseshaping(sig, beta, T=None)#

Root-raised cosine filter applied in the spectral domain.

Parameters:

  • sig (SignalObject) – input time distribution of the signal

  • beta (float) – filter roll-off factor needs to be in range [0, 1]

  • T (float, optional) – width of the filter (default: None, use the inverse of the signals symbol rate)

Returns:

sign_out – filtered signal in time domain

Return type:

SignalObject