Hi Kristoff, You can just put an additional RRC in front of it or you can calculate the tabs by folding die tabs of the RRC with themself. There is probably a numpy function to do that. Have not tested any of that, but both ways should do the trick.
Fabian Am 10. August 2021 20:44:05 MESZ schrieb Kristoff <[email protected]>: >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. > >
