[time-nuts] RF mixers for oscillator characterization, some questions

Bruce Griffiths bruce.griffiths at xtra.co.nz
Sun Apr 19 23:31:31 UTC 2009

Hej Magnus

Magnus Danielson wrote:
> Bruce Griffiths skrev:
>> Arnold
>> Arnold Tibus wrote:
>>> Bruce,
>>> a very good summary!
>>> I do not know where I can get the proposed MinCircuits DBM here, I
>>> looked to all the big and international well known supplier of
>>> electronics parts with negativ result.
>>> If I have to import them from USA they could end up even above 100 $
>>> ea. we have in Europe to take the high shipment costs and the 19%
>>> VAT into account. 
>>> Is it likely to get used mixers with damaged diodes?
>>> Did somebody alredy look inside the metal case of the 10514A?
>>> Will it perhaps possible to reconnect the common ground connections
>>> such a way that the mentioned loops can be opened?
>> Not without changing the IF port connector or at least insulating its
>> shell from ground.
>> It may be easier just to construct you own mixer if you cant easily
>> obtain the PCB mount Mincircuits mixers that have separate IF and RF
>> grounds.
> Bruce, many SMD mixers also have separate LO, IF and RF grounds. It is
> just not documented in the datasheets. The recommended footprint
> pattern (on say RMS-5+) actually ties them together. The MiniCircuit
> SMD mixers I have been able to investigated (some of them have open
> bottom, so looking in just takes a sharp eye) is not hooked up with a
> internally forced common ground. A simple DC resistance measurement
> would indicate if a particular model has their grounds connected
> together, but really, they should fix their datasheets. I guess it
> just haven't been important for them before.
Yes its likely that at least some SMT mixers have isolated grounds,
however not all will.

In particular all Minicircuits SMT phase detectors appear to have a
common ground:
The bottom view of the SYPD series phase detectors (attached) seems to
indicate that all grounds are connected together internally (or at least
externally on the package).

>> Another alternative is to use a couple of RF transformers to isolate the
>> mixer common ground from the RF source grounds and just have the mixer
>> IF port grounded via its coax cable.
>> If necessary you can easily wind you own RF transformers if you can
>> obtain suitable ferrite cores.
>> I thought that there was a Minicircuits distributor in
>> Germany(http://www.municom.de/products/products960.php).
>> Ulrich may know more about this.
> Actually, MiniCircuits web indicates two.
> Cheers,
> Magnus
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