Time synchronization problem with "niUSRP EX Rx Multiple Synchronized Inputs.v i " ??

[USRP]

Hello,  

I used "niUSRP EX Rx Multiple Synchronized Inputs.vi "( offred by NI) to synchronize 2 USRP in reception (the master connected to laptop via Ethernet and the slave connected to the master via MIMO cable). 

I set: master--> RefIn and PpsIn     slave-->Mimo and Mimo. 

Problem: Inspite I used identical cables that connect the both devices to the transmitter; the signal received by the master and the signal received by the slave ar'nt synchronized in time because the time lag (delay) is not constant!!!. 

Where is the problem?!!  

Thank you

[ErikL]

Is it phase difference or time lag?  Can you submit a screen shot?

[USRP]

Hi,

Yes, it's the time lag.

I must have a constant time lag or time lage equals to zero.   

i did two simulations.

Best regards

[ErikL]

You are observing phase offset not time lag. The signals that you're working with our RS downconverted signals. To see only the time relationship between the two signals you will need to plot the complex magnitude.

You can do the following experiment. You can actually set the transmitter to transmit some fractional second after the Receiver begins. When you do that you'll see that there are no sine waves and all of a sudden they appear. The fact that they are some waves and their frequency are related to the LO phase and not theme alignment.

[ErikL]

For example, just moving the antennas around will allow you to modify the phase.

Here is a great example to play with this:
https://decibel.ni.com/content/docs/DOC-19209

You can see the constellation rotate but time stay the same as you move the antennas.

[USRP]

Hi,

I used:

transmitter--> Rohde & Shwartz SM300 signal generator.

Receivers-->  2 x USRP N200 (connected with MIMO cable)  master--> RefIn and PpsIn     slave-->Mimo and Mimo.

3 identical cables to transmit the signal, connected via Power Splitter/Combiner (Mini-Circuits).

Cable 10MHz connects the master device with the transmitter.

 FreqTx=700MHz  (sin)           CarrierFreqRx=701MHz  --------> so the received signals are a sin of 1MHz (701-700=1MHz).

I have no probleme with phase synchronisation (because both the slave and the master received a sin of 1MHz).

My problem is the time synchronization:

How can I verify if i did the  time synchronization?

I must have 2 superposed sin [(ch0 I with ch1 I) (ch0 Q with ch1Q)] ?

I must do Timed commands? if yes! How to do it?

I try to run the example of constellation, then i have message: Find VI Named".........Vi"    I have this problem all the time when I run some examples . I have probleme with setup LabView?!

Best regards