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Re: [Discuss-gnuradio] porting ATSC to 2.x and USRP

From: Eric Blossom
Subject: Re: [Discuss-gnuradio] porting ATSC to 2.x and USRP
Date: Tue, 21 Mar 2006 16:39:16 -0800
User-agent: Mutt/1.5.9i

On Tue, Mar 21, 2006 at 02:41:29PM -0800, mao mao wrote:
> Here's why I don't want to use USRP to handle ATSC:
> If the captured ATSC stream is 16Ms real data and the
> IF is 4MHz, then the freq range of the ATSC signal
> will be 1MHz to 7MHz, and the pilot freq Fp will be
> 1.31MHz.
> If I use the FPLL code in gnuradio 0.9, to move the
> pilot freq to zero, I have to multiply the sample data
> with the NCO clock, which is 1.31MHz, this way, I'll
> get two sets of signals mixed together, one set has
> the freq range of -0.31MHz to 5.69MHz, the other set
> has the freq range of 1.31MHz to 6.31MHz. 
> Here's the BIG problem: You can't use low pass filter
> to kill the second set of signals without unhurting
> the first set. So the FPLL codes in gnuradio 0.9 WILL
> NOT work on USRP's 16Ms data.
> When you use 20Ms data with 5.75MHz IF, the pilot
> frequency FP is 3.06MHz. If you multiply the sample
> data with NCO, you also get 2 sets of signals: one is
> -0.31MHz to 5.69MHz, the other set is 5.81 to
> 11.81MHz. So in this case, you can get rid of the
> second part with a simple Lowpass filter.
> This is the reason why I don't want to use USRP to
> handle HDTV. I will be really glad if someone can
> provide a working way to recover the ATSC carrier with

OK.  Good points.  

Here's a proposal: if you, Rafael, or anybody else, get the rest of
the code ported (following the outline about the loopback tests in the
previous message), I will ensure that the FPLL is modified to work
with complex baseband from the USRP.


I've created a directory (gnuradio-examples/python/apps/atsc) to hold
the test code and atsc tx and rx apps.  If you accept my proposal,
I'll also enable the building of those parts of gnuradio-core/src/lib/atsc
that already work under the 2.x framework.  The rest as they say, is
left as an exercise ;)

Actually, it would be better if I moved it all into a new gr-atsc CVS
module. Then we could set up whoever was working on the port with
commit access to the gr-atsc code.

It would be great to have the ATSC code ported to 2.x and using the
USRP.  This would enable anybody with a USRP and TV_RX board to begin
experimenting with HDTV.

Do we have any takers???  


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