Uwe, A Costas receiver does what I think the 5120 does. You can buy one, called a software defined rario, for less than $1000. It consists of two double-balanced mixers converting to baseband. The I and Q signals are sent to a 24-bit sound card and ordinary PC. The rest is done by a DSP program, which does the filtering and combining. What makes this a Costas receiver is that the synthesized local oscillator generates the I and Q mixer signal 90 degrees out of phase and the I and Q channels baseband processing has to by 90 degrees out of phase as well, which is the hard part. The sound card of course has a lower frequency limit of a few Hz; it really should use direct-coupled ADCs.
The result is exactly equivalent to an SSB receiver, which reveals the baseband phase noise and anything else that gets in the way. Do a fast Fourier transform and see the dBc characteristic. Not really very novel and I would think not patentable due prior art. Do you know the patent number or name? Dave Uwe Klein wrote: > Joseph Gwinn wrote: > >> In article <[EMAIL PROTECTED]>, >> Uwe Klein <[EMAIL PROTECTED]> wrote: >> >> >>> Joseph Gwinn wrote: >>> >>>> I may need a Dual Mixer Time Difference (DMTD) instrument, to >>>> measure picosecond changes in electrical length in a coax plus >>>> amplifier time reference signal distribution system with total >>>> delays in the hundreds of nanoseconds, currently operating at 10 MHz >>>> (sinewave), but with 100 MHz likely at some future date. >>>> >>>> What DMTD instruments are commercially available? A google search >>>> was not successful - all noise no detectable signal, probably >>>> because DMTD instruments are not that common, and many people build >>>> their own. >>>> >>>> Thanks, >>>> >>>> Joe Gwinn >>> >>> >>> Take one of the "better" GS DSO's that have high storage depth. >>> Read the shots from the DSO and do all further processing in software? >> >> >> >> I don't understand how this would work. Could you expand the >> description? And what is "GS"? > > GS as in GigaSample > >> > http://www.unusualresearch.com/AppNotes/TimeNuts/OptDualMixer.pdf > http://www.wriley.com/paper6ht.htm > > if my understanding is correct: > take a large syncronous sampling of both signals. > extract the data. > retrace in software the math done in hardware on the aquired data set. > i.e. if you do a soft mixdown to DC you should get two vectors (R/I) > describing the phase relationship between both signals. > > uwe _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
