Dr Bruce Griffiths said the following on 02/04/2007 02:32 AM: > My calculations using the component values in the circuit indicate that > the TADD-1 noise figure should be about 19dB and its corresponding phase > noise floor should be lower than -160dBc/Hz. when the input signal is > +7dBm or greater. So unless you had an unusually noisy set of opamps > and/or resistors the measurement setup phase noise floor probably > exceeds that of the TADD-1 by around 20dB.
Thanks for running that calculation, Bruce! I am somewhat suspect of our test setup as the fellow who owned the 3048 had never done this type of measurement before. I also don't recall just what the input level was for our test. In the next month or so, I'm hoping to rerun the measurements with an easier-to-use, if not actually better, phase noise system and will report those results. > With a 10V supply instead of 9V and a +13dBm input the phase noise floor > should be about -168dBc/Hz which is respectable but a few (~10) dB shy > of the state of the art. > > The only way to achieve the state of the art performance with opamps > using a 9 or 10V supply is to use lower noise (2nV/rtHz appears > feasible) opamps pairs driven in push pull by an input step up (1:2 > turns ratio) transformer with an output stepdown transformer driven in > pushpull by the 2 opamp outputs. The noisy 1K input protection resistor > would also have to be reduced in value as would the opamp feedback > network resistors. > > NIST's 1995 distribution amplifier claims a phase tempco of 0.3ps/K and > 120dB isolation between channels. > http://www.physics.nist.gov/News/Update/950626.html > > Bruce > > _______________________________________________ > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts