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Re: [Discuss-gnuradio] Frequency dependent problem after syncronizing ,
From: |
Johnathan Corgan |
Subject: |
Re: [Discuss-gnuradio] Frequency dependent problem after syncronizing , Please help! |
Date: |
Thu, 12 Feb 2009 10:33:16 -0800 |
On Thu, Feb 12, 2009 at 5:43 AM, Bruhtesfa Ebrahim <address@hidden> wrote:
> I syncronized my USRPs(one is v4.3 and the other v4.5) by using the USRP
> clocking notes on http://www.gnuradio.org/trac/wiki/USRPClockingNotes,
> to make them frequency and phase syncronized.
Ok.
> ...Then,I run usrp_fft.py on the master USRP.I
> see that the master USRP receives the 5GHz transmission from signal
> generator without problem, but when i change the center frequency to
> 4.96GHz to receive from the slave, I got a weird signal.The signal is
> not stable, the noise(whole spectrum) level decreases and increases very
> fast and it has only a very small peak at the center frequency.Moreover,
> the spectrum changes very much with gain.)
It sounds like, since you have perfect synchronization between
transmitter and receiver, that what you have after downconversion in
the daughterboard is DC + noise. That is, the transmitted carrier
(plus noise and multipath from the channel) is being mixed with a
synchronized local oscillator, resulting in only the noise components
being left in the complex baseband signal GNU Radio is receiving.
There will also be a DC component based on the path delay and
wavelength causing a phase shift between the transmitted carrier phase
and and the receiver LO phase.
Johnathan
- [Discuss-gnuradio] Frequency dependent problem after syncronizing , Please help!, Bruhtesfa Ebrahim, 2009/02/12
- Re: [Discuss-gnuradio] Frequency dependent problem after syncronizing , Please help!,
Johnathan Corgan <=
- [Discuss-gnuradio] Re: Frequency dependent problem after syncronizing , Please help!, Bruhtesfa Ebrahim, 2009/02/12
- Re: [Discuss-gnuradio] Re: Frequency dependent problem after syncronizing , Please help!, Johnathan Corgan, 2009/02/12
- [Discuss-gnuradio] gnuradio mentioned in cnet article on phone snooping, ematlis, 2009/02/12
- Re: [Discuss-gnuradio] Re: Frequency dependent problem after syncronizing , Please help!, Eric Blossom, 2009/02/16
- [Discuss-gnuradio] Re: Re: Frequency dependent problem after syncronizing , Please help!, Bruhtesfa Ebrahim, 2009/02/16