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From: | mleech |
Subject: | Re: [Discuss-gnuradio] mimo beam forming on USRP |
Date: | Tue, 03 Mar 2015 11:18:57 -0500 |
User-agent: | Roundcube Webmail/1.0.2 |
If you use the phase-resynch feature of the SBX card, and you have common refclock and 1PPS across all your USRPs in the array, In *general*, synthesized downconverters use fractional-N synthesizers where their starting phase after a re-tune is random with respect to any other synthesizer using the same reference clock. That's just the way fractional- N synthesis works. It happens that SBX uses an ADF4351 synthesizer, which has a (rare!) hardware feature to allow phase-resynch after tuning. In order to make this work, all SBXes in your "array" must be tuned at exactly the same time, so the timed_commands feature must be used to do the tuning. See: http://files.ettus.com/manual/page_sync.html
On 2015-03-03 11:05, Pengyu Zhang wrote:
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