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Re: [Discuss-gnuradio] unknown phase-relation between rx and tx
From: |
wolfgang buesser |
Subject: |
Re: [Discuss-gnuradio] unknown phase-relation between rx and tx |
Date: |
Sun, 22 Jun 2008 03:58:21 -0700 (PDT) |
Just to make sure:
I am using LF RX/TX-boards.
TX and RX are on the subdev (thus using the same AD9862)
Thanks
Wolfgang
Jonathan Friedman-2 wrote:
>
> Unless I misunderstand what you are doing, what you are describing is
> the coherence error of the system. The long-answer made short is "no".
> You have to calibrate it out or otherwise live with it. The TX and RX
> paths of the USRP are derived from separate hardware local oscillators
> so there will always be an unknown phase error between them. What's
> worse is that it will vary slowly and dynamically as temperature and
> voltage change during system operation.
>
> Cheers,
> -Jonathan
>
> On Sun, Jun 22, 2008 at 2:42 AM, wolfgang buesser
> <address@hidden> wrote:
>>
>> Hi,
>>
>> Iam using
>> gr.sig_source_s (self.usb_freq (), gr.GR_CONST_WAVE, 0, 0, 0)
>> to generate a carrier and
>> usrp.source_c(nchan=2,decim_rate=self.interp) to resample it at the
>> same
>> frequency.
>>
>> I get what I expect: 2 complex numbers which are pretty constant. But
>> with
>> every restart
>> of the program the phase changes (apparently by the same amount for both
>> channels). The
>> amplitude does not vary much from run to run.
>>
>> It seems to me, that the phase relation between the interpolator in the
>> TX
>> and the decimator in
>> the RX changes with every restart.
>>
>> Is there a way to "reset" the interpolator/decimator so that I get the
>> same
>> reading for every start
>> (as long as I don't change frequencies) ?
>>
>> Thank's
>> Wolfgang
>> --
>> View this message in context:
>> http://www.nabble.com/unknown-phase-relation-between-rx-and-tx-tp18052839p18052839.html
>> Sent from the GnuRadio mailing list archive at Nabble.com.
>>
>>
>>
>> _______________________________________________
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>>
>>
>
>
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>
--
View this message in context:
http://www.nabble.com/unknown-phase-relation-between-rx-and-tx-tp18052839p18053437.html
Sent from the GnuRadio mailing list archive at Nabble.com.
Re: [Discuss-gnuradio] unknown phase-relation between rx and tx, Eric Blossom, 2008/06/22