TX RX synchronization in the same vi

[qdlpavel]

Hi guys,

       I am working on a software defined radar. When I put the TX and RX blocks in the same VI, I cannot make them synchronized. 

       Here is what I did: I configured the same timestamp to both TX and RX sessions and set both sessions the same time. But the received signal shows that the delay changes frequently, which means the TX and RX sessions are not started simultaneously, and the delay changes everytime. Is there any way to make transmission and reading start at exactly the same time?

[PeanutButterOven]

qdlpavel,

When you say Tx timestamp are you referring to a timestamp generated in the software loop?

[qdlpavel]

The timestamp is wired to the "niUSRP Configure Trigger" block, as 2 second. And the other is wired to the "Set Time" block as 0 second.

I just got them synchronized. The reason the delay is changing is caused by too high IQ rate. As the error status is not extracted or wired to the termination in the while loop, it started transmitting data ocassionally.

But the result shows that there is still 3 us delay. Does any one know how to eliminate this part?

Thank you so much. 

[PeanutButterOven]

yes thats great, if you follow the example Rx Finite Sync and Tx finite sync they show how to timestamp correctly. The 3us delay is normal for the harware. I tested the setup with an NI 2920 and received anywhere from 2us-4us consistently.  

[qdlpavel]

I get it. Thank you so much!

[PeanutButterOven]

I took a look at the schematics and there is some analog baseband filters that will cause a slight delay. Just fyi