[time-nuts] Nifty "MINI TIC" for DMTD work detail Info please read

[Bob Camp]

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.griffiths at 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
>> 
>> EWKehren at 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.griffiths at xtra.co.nz writes:
>>> 
>>> EWKehren at 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 at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.