Hi, In our application we need to emit pure tones on two RFX400 daughtercards sitting on the same USRP board. More importantly, the phase of the two RF carriers need to be in sync or should have a deterministic difference. I put together a simple experiment (GnuRadio 3.1 release branch r8117, USRP rev 4.5, FLEX400 10-11-05) which sends a pair of constant signals to the USRP in the baseband. The RF transmit outputs are directly connected to a scope (5GS/s, 50 ohm imp.). My problem is that the phase relationship between the two sines is random and changing every time I run the python script. I suspected that the DUC(s) in the CODEC chip(s) cause this, so I was trying to "turn them off" by modifying db_flexrf.py (self.set_lo_offset(0)) and using carriers where the RFX400 board can tune to without the help of the DUC. I verified with two LFTX boards that the CODECs "generate" constant outputs. Still, the RF waves have random phases, which I cannot explain (since the PLLs on the daughtercards are "driven" by the same clock coming from the USRP). Since I have very limited RF background, I need you to explain this and/or suggest a solution for the initial problem.
Thank you. -- peter _______________________________________________ Discuss-gnuradio mailing list [email protected] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
