[time-nuts] Nifty "MINI TIC" for DMTD work detail Info please read
Bruce Griffiths
bruce.griffiths at xtra.co.nz
Tue Nov 20 22:49:14 UTC 2012
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
>>
More information about the Time-nuts_lists.febo.com
mailing list