Dedispersion

New in version 0.5.

Module for calculating dispersion delay due to an ionized ISM and performing incoherent dedispersion.

lsl.misc.dedispersion.delay(freq, dm)

Calculate the relative delay due to dispersion over a given frequency range in Hz for a particular dispersion measure in pc cm^-3. Return the dispersive delay in seconds.

lsl.misc.dedispersion.incoherent(freq, waterfall, tInt, dm)

Given a list of frequencies in Hz, a 2-D array of spectra as a function of time (time by frequency), and an integration time in seconds, perform incoherent dedispersion on the data.

lsl.misc.dedispersion.getCoherentSampleSize(centralFreq, sampleRate, dm)

Estimate the number of samples needed to successfully apply coherent dedispersion to a data stream.

lsl.misc.dedispersion.coherent(timeseries, centralFreq, sampleRate, dm, taper=False)

Simple coherent dedispersion of complex-valued time-series data at a given central frequency and sample rate. A tapering function can also be applied to the chirp of the form:

,

where is the frequency difference in MHz from the band center and BW is the bandwidth in MHz.

Note

At the large fractional bandwidths of LWA, the window size needed for coherent dedispersion can be prohibitive. For example, at 74 MHz with 19.6 MS/s and a DM or 10 pc / cm^3 this function uses a window size of about 537 million point.