AnsweredAssumed Answered

Multichip RF Synchronization

Question asked by alpele on Feb 5, 2015
Latest reply on Jun 23, 2016 by BER16



I want to synchronize RX LO and TX LO of two AD9361. As stated in the user guide: "The ability to synchronize RF local oscillators between multiple AD9361 is not available. Sync between multiple chips is supported only for Baseband PLL synchronization.".


As can be seen on the figure below(from the AD-FMCOMMS5 schematic), EXT LO is used in AD-FMCOMMS5 to synchronize RX LO and TX LO. However, my operating frequency is 5.5GHz and EXT LO supports device operation up to 4GHz operating frequency. 


The phase is not important for my application, I am ok with only frequency synchronization. My approach is the same with AD-FMCOMMS5, but I am not using EXT LO. ADCLK846 is used to distribute the same clock coming from a 40MHz cyrstal, and the outputs are connected to the PLLs of both AD9361. SYNC_IN pins are connected to the ground as in AD-FMCOMMS5. The internal synthesizers are used to produce RX LO and TX LO. Can I achive the RF frequency synchronization that I desire by doing so?