bladeRF micro phase coherency

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kazam
Posts: 4
Joined: Fri Aug 10, 2018 4:24 am

bladeRF micro phase coherency

Post by kazam » Wed Oct 03, 2018 7:03 am

Hi,
Is it possible to set up two bladeRF micros such that they are phase coherent? According to AD it should be possible:Analog Devices

I'm interested in 4xRX MI applications primarily so that's why I ask.

Thanks

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rtucker
Posts: 77
Joined: Sun Jan 25, 2015 10:38 am

Re: bladeRF micro phase coherency

Post by rtucker » Tue Oct 30, 2018 7:03 pm

G'day,

Maybe! We did plan for this during design, but as far as I know, it has not yet been attempted.

From the looks of things, the FMCOMMS5 uses an ADF5355 to generate LO signals to be fed into RX_EXT_LO / TX_EXT_LO pins on the '9361s. We expose these traces on U74 (the expansion connector) on pins 3 (RX_EXT_LO) and 4 (TX_EXT_LO), so a similar sort of arrangement could be done. We also connect the SYNC_IN to the FPGA.

The FMCOMMS5 wiki section also includes a page on multi-chip synchronization, which details use of the SYNC_IN to synchronize the sampling clocks, as well as a method of using the RX*_C inputs to measure the phase error vs the other chip's TX. (We have unpopulated UFL pads for RX1_C and RX2_C, which are independent of the rest of the RF section). With a common 38.4 MHz clock connected to the CLKINs on both boards and some phase correction logic in the FPGA, it has the potential to work.

I hope this is helpful! Thanks for your question. :)
Rey Tucker (she/her)
Systems Engineer, Nuand LLC
Rochester, NY, USA

#WontBeErased

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