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AD9361 injection locking

Question asked by baudouin on Jun 15, 2016
Latest reply on Jun 16, 2016 by Vinod

Good Morning, not sure who is dealing with AD9361 technical issues at the moment but we have the following issue we could use some help with.


We are currently using the AD9631 part in a TDD system operating between 4.4 and 5GHz.

We need to use dual synth mode as switch between TX and RX has to be less than 10us.

We are finding that there is injection locking taking place between the TX synth and the RX synth which produces poor phase noise and spurs. This tends to be random depending of the phase between the TX and RX synths. If we move one synth by say 2Hz then we can see the phase noise going from back to good at this rate. The diagrams show the TX synth phase noise with the RX synth at the same frequency.


Is there any way of just using one synth but sending the output to both TX and RX chains?

Is there any way of controlling/moving the phase between the TX and RX synth carriers?


The other option is to move the RX synth by say 1MHz and demodulate with this offset.

What would be the minimum frequency separation to overcome this effect?

We have use the part at 2.5GHz before and not had a problem.


PS – Using standard Linux API