For one of my customers having few questions about the AD9361:
We are working in TD LTE and we would like to keep a constant phase of the Tx Synth and Rx Synth during Tx and Rx periods.
In order to do so we keep both Tx Synth and Rx Synth always ON and operating in the same frequency.
We noticed that in some frequencies like 5.8 - 5.9GHz the Tx Synth integrated phase noise (measured from 1KHz - 1MHz) changes from -40dBc (10mRAD) to -32dBc (24mRAD) because both Tx Synth and Rx Synth are ON. If I shot down the Rx Synth (Reg 0x015[D6] = "1") the Tx Synth integrated phase noise changes from -32dBc (24mRAD) back to -40dBc (10mRAD).
I guess that the Rx Synth integrated phase noise change as well I simply can't test it.
1. What is causing the Tx Synth integrated phase noise to change from -40dBc to -32dBc ?
During Tx we shift the Rx Synth frequency in one integer step. It solve the Tx integrated phase noise problem.
During Rx we shift the Tx Synth frequency in one integer step. It solve the Rx integrated phase noise problem.
The problem is that every time we shift the frequency the phase of the Tx Synth and Rx Synth changes.
2. Is there a way to work with both Tx and Rx Synth working in the same frequency without effecting the integrated phase noise and keeping the phase of both Synth during Tx and Rx periods ?
3. Is there a way to sync the Tx Synth and Rx Synth of two AD9361 chips ?
Thanks for your support.