[time-nuts] RF Mixers for oscillator comparison

[Bruce Griffiths]

Arnold

Some of the early equipment produced by NIST used mixers from a company
that eventually became into Minicirucits.

Suitable candidates from the Minicircuits range are:

TUF-1H+:
http://www.minicircuits.com/pdfs/TUF-1H+.pdf

This mixer doesnt have isolated RF, LO and IF grounds so external
transformers would be rrequired.
It  does have somewhat higher port to port isolation than most mixers.

The minicircuits phase detectors such as:

http://www.minicircuits.com/pdfs/RPD-1+.pdf

http://www.minicircuits.com/pdfs/MPD-1+.pdf

are worth considering, at least they have separate RF and IF grounds, a
high maximum output as well as low dc offset and offset drift.


All of these are below $US25 (at the source).

The phase detectors are perhaps the safest option however measurement of
their phase noise would be advisable.

Bruce

Arnold Tibus wrote:
> On Mon, 20 Apr 2009 09:03:36 +1200, Bruce Griffiths wrote:
>
>   
>> Corby Dawson wrote:
>>     
>>> Arnold,
>>>
>>> Look at the top of page 3 on the link below. Not sure how they arrived at
>>> their conclusion but there is one opinion on the HP mixers!
>>>
>>> http://www.unusualresearch.com/AppNotes/TimeNuts/OptDualMixer.pdf
>>>
>>> Corby Dawson
>>> ____________________________________________________________
>>> Debt collectors calling your house?  Click here to consolidate into one payment.
>>> http://thirdpartyoffers.juno.com/TGL2141/fc/BLSrjpTIk3l9oQnolYGEY40TVwmsBD4opDDeVSRG36KHWHhZWexSiuRrXdm/
>>>
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>>>       
>> Statements about the low flicker noise of these mixers are sprinkled
>> throughout the phase noise literature.
>> Someone must have measured the phase noise of these and other mixers at
>> some time.
>>     
>
>   
>> Its relatively easy to measure mixer phase noise:
>> All one needs is a low noise preamp plus a sound card a 90 degree hybrid
>> (or a suitable length of coax and a splitter) and a low noise source.
>>     
>
>   
>> However NIST papers often include a phase noise plot (attached) that
>> illustrates that high level mixers can have a significantly lower phase
>> noise than low level mixers (like the HP10514A).
>> When choosing a mixer for this for phase noise measurement applications
>> one may actually need to measure the phase noise characteristics of
>> candidate mixers.
>>     
>
>   
>> Bruce
>>     
>
>
> Wow, a good overview, Bruce! 
>
> But remain the questions: 
> which are these high level mixers, are they readily available? 
> Are they affordable? 
> Perhaps not, why are they then not applied more often?
>
> Arnold
>
>
>
>
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