Hi All, We are trying to use 4 USRPs to extract the phase information due to differences in positions of the antennas.
In a standard communications system an internally generated carrier is locked IN PHASE with the incoming signal to perform downconversion (see Figure 1.). http://old.nabble.com/file/p27838729/Fig%2B1%2BUSRP%2Bv2.jpg As mentioned above we are using 4 USRPs to receive a signal from a single source. We wish to retain the phase information of this signal between boxes due to the different positions of the antennas. We feed all 4 boxes with a clock reference signal (10MHz, 1.5Vpk-pk), so that their internal clocks should be locked in phase with respect to each other. Are the internally generated carriers generated using this clock as a phase reference, i.e. is it correct, that this should also make all the internally generated carriers have zero phase difference between the boxes instead of locking to the phases of the incoming signals (see Figure 2.)? http://old.nabble.com/file/p27838729/Fig%2B2%2BUSRP%2Bv2.jpg However, when we observe the internal clocks of 4 USRPs they are phase locked with respect to one another, but THERE IS A PHASE DIFFERENCE BETWEEN THEM, which is constant for a given power cycle. Does this imply that the phases of the internally generated carriers are locked to one another, but also with some NON 0 PHASE difference, i.e. that our actual system looks like Figure 3? http://old.nabble.com/file/p27838729/Fig%2B3%2BUSRP%2Bv3.jpg Thanks, Valentin. -- View this message in context: http://old.nabble.com/USRP-synchronization-tp27838729p27838729.html Sent from the GnuRadio mailing list archive at Nabble.com. _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
