[USRP-users] TVRX2 Automatic Gain Control problem

Lucas Kindermann lmkindermann at gmail.com
Wed Jun 20 23:11:42 EDT 2012


Hi Marcus,

Firstly, i would like to thank you for the info about the AGC configuration
and the TDA datasheet. However i'm now worried with that you've said about
the use of two TVRX2.

"Also, keep in mind that only a *single* TVRX2 can be used per USRP1 due to
I2C addressing limitations."

This is weird, because in fact i'm using two TVRX2 in one USRP1 and i can
tune both boards, although the tuned frequency for both TVRX2 channels (RX1
and RX2) is mirrored for both boards on the RXA and RXB slots. This would
not be a problem for my application because i really need that all RX
channels from both boards be tuned at the same frequency.

On Gnuradio, i can see the four channels receiving radio signals on the
tuned frequency (each channel is connected in a different antenna) and
using the uhd_usrp_probe command i can obtain the ID from both boards, each
in their correspondent slots. Presume this happens because of the data
stored at the EEPROM memory in each board.

Now my doubt is: Am i getting the two TVRX2 channels tuned each time i set
the central frequency for both boards? Or one of the boards isn't
communicating and it's tuned because the central frequency is stored in
EEPROM memory and read by the TDA receivers when USRP1 and TVRX2 boards are
turned on?

Cordially,


2012/6/20 Marcus D. Leech <mleech at ripnet.com>

>
>> Greetings,
>>
>> I'm working on a project using two USRP1 Rev. 4.5 (both USRP1 works
>> separately) and four TVRX2 Rev. 1.1 boards for DF application.
>>
>> Besides the phase alignment, this application needs the implementation of
>> amplitude detection on all RX channels too, and for this goal, the
>> Automatic Gain Control could screw up the real value of amplitude from the
>> received signals.
>>
>> Can the AGC feature on the TVRX2 receivers be shut down or manually
>> adjusted across the software configurations or hardware modifications ?
>>
>>  No, there is no way to turn off the AGC on the TVRX2.  This has been
> thoroughly investigated at Ettus, and it cannot be done.
>
>
>  Another question, i don't had success to find the full datasheet of
>> TDA18272 receiver on the internet, even at manufacturer's website. I only
>> had found a shorten version of datasheet with 10 pages that shows
>> superficially the IC's features. Do you have and could you send me a copy
>> of full datasheet or application notes of TDA18272 receiver used on TVRX2
>> design ?
>>
>> I thanks for your attention, knowing your time is precious.
>>
>>  The full datasheet is available only under NDA with NXP.
>
> Also, keep in mind that only a *single* TVRX2 can be used per USRP1 due to
> I2C addressing limitations.
>
>
>
>
> --
> Marcus Leech
> Principal Investigator
> Shirleys Bay Radio Astronomy Consortium
> http://www.sbrac.org
>
>
>
> ______________________________**_________________
> USRP-users mailing list
> USRP-users at lists.ettus.com
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>



-- 
Lucas de Mello Kindermann.
UFSC/CTC/LISHA - Software/Hardware Integration Lab.
Postgraduating in Electronics Product Development at Federal Institute of
Santa Catarina.
B.Tech in Electronics Systems at Federal Institute of Santa Catarina.
lmkindermann at gmail.com
+55 (48) 3721-9516
+55 (48) 9937-7679
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