>>
>> On Mon, Nov 14, 2011 at 9:26 AM, Tom Rondeau <
address@hidden>
>> wrote:
>> > On Mon, Nov 14, 2011 at 10:40 AM, Nowlan, Sean
>> > <
address@hidden>
>> > wrote:
>> >>
>> >> Because I need a raised cosine filter. If I convolve root raised cosine
>> >> filter coefficients with themselves (generated with gr_firdes), do I
>> >> need to
>> >> apply a scaling factor?
>> >
>> > Ok, but my question was Why do you need a raised cosine filter? I'm just
>> > curious about what applications use this instead of RRC filters?
>> > Tom
>> >
>> >>
>> >>
>> >>
>> >> From: Tom Rondeau [mailto:
address@hidden]
>> >> Sent: Monday, November 14, 2011 9:56 AM
>> >> To: Nowlan, Sean
>> >> Cc:
address@hidden
>> >> Subject: Re: [Discuss-gnuradio] raised cosine filter taps
>> >> implementation
>> >>
>> >>
>> >>
>> >> On Sun, Nov 13, 2011 at 6:56 PM, Nowlan, Sean
>> >> <
address@hidden> wrote:
>> >>
>> >> I want to add a raised cosine filter to gr_firdes.* in
>> >> gnuradio/gnuradio-core/src/lib/general/. I see there's already a
>> >> root-raised
>> >> cosine there. After looking through a few sources, I have the following
>> >> time-domain response of an RC filter:
>> >>
>> >> h(t) = [sin(pi * t / T_s) / (pi * t / T_s)] / [cos(pi * alpha * t /
>> >> T_s) /
>> >> (1 - (2 * alpha * t / T_s )^2 )]
>> >>
>> >> As far as I can tell, I should be able to compute the taps using:
>> >>
>> >> for n = -FLOOR(ntaps/2) to FLOOR(ntaps/2), do
>> >> h(n) = [sin(pi * n) / (pi * n)] / [cos(pi * alpha * n) / (1 - (2 *
>> >> alpha * n)^2 )]
>> >> end_for
>> >>
>> >> The things I'll have to worry about:
>> >> 1) if n is 0: h(n) = 1
>> >> 2) if n is +/- 1/(2 * alpha): h(n) = (1 / (8 * alpha) ) * sin(pi / (2 *
>> >> alpha) ) #I think I did this right...
>> >> 3) rounding errors: not sure what to do here given we're operating with
>> >> floats.
>> >>
>> >> Any tips/suggestions?
>> >>
>> >> Thanks,
>> >> Sean
>> >>
>> >>
>> >>
>> >> Sean,
>> >>
>> >> We've gotten this question before, and I'm again curious why you want a
>> >> raised cosine filter? If you really are using it for something, the
>> >> easiest
>> >> thing to do is just create a root raised cosine filter and convolve it
>> >> with
>> >> itself.
>> >>
>> >>
>> >>
>> >> Tom
>> >>
>> >>
>> >
>> > _______________________________________________
>> > Discuss-gnuradio mailing list
>> >
address@hidden
>> >
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>> >
>> >
>
>