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Re: [Discuss-gnuradio] QAM demod Error in GRC


From: Tom Rondeau
Subject: Re: [Discuss-gnuradio] QAM demod Error in GRC
Date: Wed, 25 May 2011 10:00:27 +0100

On Tue, May 24, 2011 at 5:29 PM, Colby Boyer <address@hidden> wrote:
On Tue, May 24, 2011 at 3:13 AM, Tom Rondeau <address@hidden> wrote:
> On Mon, May 23, 2011 at 10:37 PM, Ben Reynwar <address@hidden> wrote:
>>
>> On Mon, May 23, 2011 at 12:09 PM, Josh Blum <address@hidden> wrote:
>> >
>> >
>> > On 05/23/2011 03:29 AM, Vlad Stoianovici wrote:
>> >>
>> >> Dear Marcus and Bob,
>> >> I did understand that the block was hollow, but this thread is kindda
>> >> old,
>> >> so I thought that in the mean time maybe someone implemented the code
>> >> and
>> >> functionality you are referring to.
>> >> I'm using GRC, but I don't have time to start learning python with the
>> >> sole
>> >> purpose of being able to write the QAM block.
>> >> It would probably be easier to use Simulink, which I'd rather not do.
>> >>
>> >
>> > This is a motivating example for a new gr-digital component that can
>> > make use of tags: the QAM deframer block. :-)
>> >
>> > -josh
>>
>> In the psk8 branch of my github repo
>> (www.github.com/benreynwar/gnuradio/) there is QAM modulation and
>> demodulation within the "digital" category of GRC.  I haven't tested
>> it recently though.  Let me know if you try it and it doesn't work.
>>
>> Cheers,
>> Ben
>
> Ben's branch is based off of my 8psk branch in github, too. I still need to
> pull in his changes. I have a feeling we might be going back and forth a bit
> in the development of the gr-digital top-level directory. This will make it
> into the upcoming 'next' branch for the 3.5 release.
> Currently, it includes a more robust version of the Costas loop (you specify
> the natural freq and damping factor instead of the gains; it sets the gains
> properly so that the system is more tolerant and locks better) as well as a
> reworking of the CMA equalizer. I have yet to use this equalizer on a real
> signal, only simulated multipath channels, so more experience would be good.
> Note that if you are using this branch you should --disable-gr-trellis. I
> banged up the API that is used in gr-trellis and haven't got back to fix it,
> yet.
> Tom
>

Tom, somewhat related.

In the next week or so (when I have time), I will be contribute a
Gardner timing sync block to GNURadio. It should be a nice addition
for the DxPSK blocks, as it is carrier phase independent.

--Colby


Thanks, Colby, it'd be good to have that one in the toolbox. The M&M loop and PFB clock sync blocks are also phase independent, though :)

Tom


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