On 11/01/12 06:56 PM, Armando Rocha wrote: > Dear all > > I am using USRP1 with two basic RX daughter boards and two input > signals (one at each Basic RX) with the same frequency. > > The two 10. 7 MHz signals cartesian components: > - (I1, Q1) from one channel of the 1st Basic RX card > - (I2, Q2) from the 2nd Basic Rx card > are mixed with the NCO at about 10.7 MHz to almost DC, decimated and > sent to PC. > > The PC software computes the received signal frequency, amplitudes and > the relative phase that remains constant along the time if the NCO > frequency is not changed. > > To compensate frequency drifts the NCO is periodically adjusted by > reprogramming the two devices." using the tune function. > > After this reprogramming however the relative phase between the > signals often (but not always) changes a lot (not always the same > phase change). > > A detailed suggestion to solve this problem is appreciated as accurate > phase measurement is important in my application (I can not find a > clear response to this issue in the discussions). > > The NCO reprogramming isn't, as far as I know, phase-continuous. Josh and/or Jason could likely comment, but my understanding is that phase is only left unperturbed when you leave the frequency intact.
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