Hi A pair of common base amps will get you to what ever your layout will permit. A single common base at 10 MHz should get you to at least 60 db with a little care. If you run a reasonable transistor you can run levels that will fry a 10 or a 13 dbm mixer. Again, all the discrete circuits work pretty well. It's the modular stuff (especially when driven hard) you have to watch out for.
Bob On Nov 21, 2012, at 1:43 AM, Bruce Griffiths <bruce.griffi...@xtra.co.nz> wrote: > > Reverse isolation at 10MHz is around 43dB. > This can be improved significantly by using a Sziklai pair instead of a > single transistor in each amplifier. > However one could also do this in a CB amp. > > Since phase detectors require LO and RF input levels of around 10dBm either > deign should suffice. > NIST have shown that high level mixers appear to be somewhat noisier than > either the ZRPD1 and 10534A. > Whilst their custom mixer utilising diode connected 2N222A's has the lowest > flicker noise the increased PCB board complexity may not be worthwhile for > this application. > Reducing the isolation amplifier noise contribution should be more effective > than any other changes to the DMTD design. > > Bruce > > Bob Camp wrote: >> Hi >> >> A few more parts and likely not quite as much isolation. None of that means >> it won't do a good job though. >> >> Bob >> >> On Nov 20, 2012, at 11:20 PM, Bruce Griffiths<bruce.griffi...@xtra.co.nz> >> wrote: >> >> >>> The attached circuit is somewhat more efficient and a little quieter. >>> With a little elaboration lower distortion is possible. >>> >>> Bruce >>> >>> Bob Camp wrote: >>> >>>> Hi >>>> >>>> Given that common practice is to mis-match the IF port on the mixers, it's >>>> probably not realistic to depend on exact match for isolation. Simple / >>>> cheap common base buffers likely are a better approach. Lots of isolation >>>> and not much flicker noise. >>>> >>>> Bob >>>> >>>> On Nov 20, 2012, at 9:01 PM, Bruce Griffiths<bruce.griffi...@xtra.co.nz> >>>> wrote: >>>> >>>> >>>> >>>>> The details about matching (if any) used in the Czech DMTD would be >>>>> informative. >>>>> >>>>> To avoid degrading the performance of the DMTD system below that imposed >>>>> by the mixers any isolation amps used will need a flicker phase noise >>>>> floor below that of the mixers. >>>>> Even an opamp based isolation amplifier can be at least 10dB quieter (for >>>>> offsets of 10Hz and below) than a typical minicircuits RF amp. >>>>> This is still about 10dB or so worse than a good mixer. >>>>> A well designed low gain isolation amp built with discrete transistors >>>>> can have significantly lower additive phase noise than an opamp. >>>>> >>>>> To reduce the DMTD system noise one can either: >>>>> >>>>> 1) Carefully match all ports using series resistors, pads etc as >>>>> necessary to achieve the required isolation together with a high output >>>>> low flicker phase noise amplifier to drive the splitter >>>>> >>>>> 2) Use isolation amplifiers with very low flicker phase noise. >>>>> >>>>> Some isolation between the 2 RF inputs of a DMTD is usually necessary to >>>>> avoid injection locking of the 2 sources being compared. >>>>> >>>>> >>>>> Bruce >>>>> >>>>> Bob Camp wrote: >>>>> >>>>> >>>>>> 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. >>>>>> >>>>>> >>>>>> >>>>>> >>>>> _______________________________________________ >>>>> 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. >>>> >>>> >>>> >>> <DualCEBuffer3.gif>_______________________________________________ >>> 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. >> >> > > > _______________________________________________ > 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.