Seems fine, should work :)
Am 10. August 2021 22:44:44 MESZ schrieb Kristoff <[email protected]>: >Hi Fabian, > >Thanks, i'll try both options and compair them. > > >I remember from my books on DSP it is possible to combine multiple >consecutive FIT filters into one, so I did a little bit of more research >on this. > > >I found (*) that -as convolution as associative- this implies this: > >(( f * h1) * h2) = f * (h1 * h2) > > > >So I guess I just use firdes.root_raised_cosine to calculate the RRC and >then "numpy.convolute()" it with itself, I should get the RC. > >Feel free to correct me if I am wrong. :-) > > > >(*) >https://dsp.stackexchange.com/questions/20194/concept-of-combining-multiple-fir-filters-into-1-fir-filter > > >Kristoff > > > >On 10.08.21 21:01, Fabian Schwartau wrote: >> 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 >> <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 >> <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. >> >>
