In message <[EMAIL PROTECTED]>, John Ackermann N8UR writes: >Poul-Henning Kamp wrote: >> Has anybody considered using the GNURadio USRP to measure Allan >> variation and phase-noise of signals ? >> >> It can sample two input signals at high resolution and speed >> so it should be almost ideal for our purposes... >> >> http://comsec.com/wiki?UniversalSoftwareRadioPeripheral >> > >I've *considered* it, but haven't done anything about it yet :-). > >I do have one of the USRP units, and it is a highly cool piece of >hardware. The whole system (including the four ADCs, each >64msample/sec, 14 bit) is clocked from a single 64MHz oscillator, and >provision is made to replace the on-board oscillator with an SMA jack.
That wouldn't really be necessary I think, because since the USRP has two inputs you can feed your reference to one and the signal you want to measure to the other and the 64MHz signal factors out in the math. (For other purposes it would be cool to have it PLL-locked to atomics) The idea I have is something like this: Calculate the phase difference between the two signals as a function of time. Any linear component to that is a frequency difference and it should be eliminated. A FFT of the residual gives the phase noise or the allan variance could be calculated from it. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
