Sending CW between individual transmissions of data

[Vojtech_D.]

Hi,

I would like to set USRP to a mode, in which it keeps sending CW until it has been triggered for next transmission of user-defined data using niUSRP Write TX Data.vi. The background is following: I define data, send them and receive and while processing the received data and preparing them for next transmission I need to keep the CW on. Is there a way to do this?

Best regards,

Vojtech

[Anthony_F]

Hello Vojtech,

What you need would be similar architecure as the TDM example that was recently posted.

Instead of feeding zeros to the USRP for IQ pairs, you would need to send some other constant value such as 0.5 or 1.0 and keep a constant stream of IQ pairs transmitted to the USRP to prevent buffer underflows

[Vojtech_D.]

Hi Anthony,

Thank you for your suggestion. From the TDM example I understood that I need to keep two parallel loops running. The CW loop will be sending 1.0 while I am computing data for the next transmission. When done, the Data-loop triggers transmission of the prepared modulated data. Was my understanding correct? If yes, would there be a solution available, which would be done on lower level (driver-level)? Let's say I send some IQ data to USRP, which stores them internally and once triggered it will keep resending the IQ data until the user terminated this?

Vojtech

[Anthony_F · Accepted solution]

Hello Vojtech,

That analysis is very good and is correct. Unfortunately there does not exist and low level driver functions to handle this scenario. The USRP does not have named waveform capabilities like our vector signal generators, so all IQ waveforms would need to be loaded in a continuous manner.