I have the FPGA based microwave modem based upon ADF5355 synthesators. This synthesators used in transmitter and receiver. I connect the transmitter with receiver, set the same frequecty and see the radio link. But there is the problem: each 2-5 seconds there is constellation phase jumping.
I spend some time to diagnose the board and have some observations:
1. It's not a FPGA receiver loop problem. Because if i replace synthesators based upon 5535 by synthesators on the other chip's all is fine.
2. It's not a impulse power supply problem. Because i remove all impulse power sources by linear and there is no any changes
3. It's not a reference generator problem. I use Rakon TCXO225BT-25MHz generator with good phase noises and stability. Moreover I place two this generators near the 5535 chips, No any changes.
I'm confused. What's happend? It's look like there is 5535 VCO changes during work or autocalibration is switch on during work.
Maybe somebody have any idea about this sitution? Thank you.