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Re: [Discuss-gnuradio] Re: How to syncronize 2 XCVR2450 daughterbords

From: Matt Ettus
Subject: Re: [Discuss-gnuradio] Re: How to syncronize 2 XCVR2450 daughterbords
Date: Thu, 05 Feb 2009 09:58:38 -0800
User-agent: Thunderbird (X11/20090105)

Bruhtesfa Ebrahim wrote:
Jason Uher wrote:
So, could you explain me how to syncronize these boards to use same
oscillator and where can i get detailed information about the steps to
make it.
Also, is there some other way to decrease phase noise between



The instructions for linking the clocks are here:



But I am confused with one thing.

I have read that the VCO on daugherbords uses PLL frequency synthesizer by using the USRP clock as a reference. If I syncronize the two USRPs(to work as a master and slave), will the Daughterboards,XCVR2450 operating on them become frequency and phase synchronized?

YES.  That is the whole point.

Each XCVR2450 has its own local oscillator which is locked to the master clock on the USRP motherboard. You can make both USRPs share the same master clock by following the directions above. You CANNOT make both XCVRs use the same local oscillator, you can only make them lock their own LOs to the master clock. However, both will then produce phase-locked, frequency-locked output.

Also on the USRP clocking notes, a step is desribed to "disable the daughterboard clock and enable the motherboard clock". So, which is the reference for the PLL frequency synthesizer by default, the daughterboard clock or the motherboard clock?

That does not apply to you. That is for old RFX boards, not XCVR2450 boards.


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