A raised cosine is also known as a Hann window. https://www.gnuradio.org/doc/doxygen/classgr_1_1fft_1_1window.html#a599d7e9625d6cc77203a8b877c4911e2a0099ec5d7a2ab5d7a7f3fd7f7835c72a
Example usage: https://github.com/bitglue/gr-radioteletype/blob/3a00e28a2c83b45e9252da41802dcbe30decc49a/python/radioteletype/filters.py#L161-L170 On Tue, Aug 10, 2021 at 12:46 PM Kristoff <[email protected]> wrote: > Hi all, > > > I am playing around with PSK demodulation, now doing a small project > trying to decode the slow-speed PSK data on the 198 KHz carrier of BBC > radio 4. > > The specs are here: > http://downloads.bbc.co.uk/rd/pubs/reports/1984-19.pdf > > According the document (page 2 of the document, page 8 of the PDF), the > system uses a shaping-filter of cos(pi * f * Td / 4). > (with Td = 50) > > If I am correct, this is in fact a raised-cosine filter with beta = 1. > https://en.wikipedia.org/wiki/Raised-cosine_filter > > So the document seems to specify a raised-cosine filter, both on the > transmit and receive side; so not a ROOT raised-cosine as is used in > most PSK systems. > > Question:| > How do I create the filter-taps for the Polyphase clock sync block for a > raised-cosine filter? > > I found a function firdes.root_raised_cosine, but no firdes.raised_cosine? > > Is there a way to easily convert the taps of a RRC filter to those of a > RC filter? (RC = RRC^2, so square the value of all taps?) > > > > Any other ideas? > - put an additional RRC low-pass filter in front of the Polyphase > clock-sync block? > - use firdes.pm_remez() ? > > > > Thanks in advance, > > > Kr. > > >
