Hi Those isolation numbers are *highly* dependent on very good matching at all ports. That's rarely the case unless you have a bunch of pads running around the system.
Bob On Nov 20, 2012, at 5:49 PM, Bruce Griffiths <bruce.griffi...@xtra.co.nz> wrote: > Typical Minicircuits SMT RF amps have a phase noise at best 20dB worse (@10Hz > offset) than the mixer/phase detector. > Their reverse isolation is quite low (<<40dB) > > The principle reason that the Czech DMTD has such low internal noise is due > to the absence of any isolation amplifiers. > They use the outputs of a 2 way splitter to drive the LO inputs of the mixers. > > A output to output isolation of 40dB or more at 10MHz is possible with some > minicicuits splitters (e.g. SYPS-2-1). > The ZRPD1 has an RF1 - RF2 isolation of around 70dB at 10MHz. > > With a channel to channel isolation of around 110dB for a 2x ZRPD1 + Splitter > combination isolation amplifiers may not be necessary. > > Bruce > > Bruce Griffiths wrote: >> Since mixer noise is one of the limiting factors using a mixer with low >> flicker noise will help. >> NIST found that a custom mixer using diode connected (collector base short) >> 2N222As had a significantly lower flicker phase noise than either the ZRPD1 >> or the 10534A. >> They used off the shelf 1:5 impedance ratio transformers (probably from >> Minicircuits). >> Another issue is the flicker phase noise of any isolation amplifiers used. >> This is particularly critical if each mixer uses its own isolation >> amplifiers. >> >> My current amplifier phase noise measurement setup (for measuring the >> additive PN of a pair of well matched amplifiers) has a self noise of around >> -170dBc/Hz @ 1Hz offset for a 10MHz input. >> Ideally the additive phase noise of any isolation amplifiers should be well >> below that of the mixers. >> >> Bruce >> >> ewkeh...@aol.com wrote: >>> Yes Bruce I have the paper. I am not suggesting to copy it verbatim but if >>> there is a way to reach reasonable priced 1 E-14 members of the list should >>> pipe in. I am willing to do an other board. the rest of the systems well >>> on its way. Einally after three years. >>> Bert Kehren >>> >>> >>> In a message dated 11/20/2012 3:28:57 P.M. Eastern Standard Time, >>> bruce.griffi...@xtra.co.nz writes: >>> >>> ewkeh...@aol.com wrote: >>>> The D/M is being revisited because of the counter performance. 1 E-13 is >>>> easily attainable but the Czech IREE published a paper and claim 2 E-15. >>>> >>> Do you mean the paper ""optimization of dual-mixer time-difference >>> multiplier" ? >>> The ZCD developed in this is a bit of a kludge and is far from optimum. >>> Reverse engineering the circuit from the description given in the paper >>> isn't too difficult. >>> They claim an instrument limited ADEV of ~7E-15 @ 1s. >>> Do you have a copy of this paper? >>>> Bert Kehren Miami >>>> _______________________________________________ >>>> >>> Bruce >>> > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
