pkern:
Maybe I find the reason for the reflection. I use HMC910 in previous of AD9525. Each pin of output diff. driver of HMC910 is connected to VCC via a 50 ohm resister, as the picture below shows. So the differential impedance between of QN and QP of HMC910 is100 ohm. When I use the termination as PIC1 before AD9525, I see reflection as PIC2 shows.
The question is how should I terminate the signal before AD9525 while I use HMC910 in previous of it?
By the way, while I get rid of the 100 ohm resistor in pic1, reflection still exist.
Thanks
Jacky
2014-04-12