[time-nuts] Phase noise test set reference articles

Magnus Danielson magnus at rubidium.dyndns.org
Tue Mar 29 19:33:06 EDT 2016



On 03/30/2016 12:28 AM, Gerhard Hoffmann wrote:
> Am 29.03.2016 um 16:53 schrieb Charles Steinmetz:
>>
>> (10)  Phase_detector_with_low_flicker_noise_BARNES_etal_NIST_2011:
>> Describes a DIY double-balanced mixer phase detector using
>> diode-connected 2N2222 transistors.  [Note that only the flicker noise
>> is improved -- the white noise floor is actually significantly higher
>> than with DBMs using diodes.  NB: There are much better transistors
>> than the 2N2222 for this application.]
> .. and they are NOT really used as diodes. They are used as switching
> transistors with most current flow C-E, saturation enforced.
> That turns faster on than the diode exp-law.
> Somewhere they also say that they use 50 Ohm load.
>
> I really wonder where all that ring mixer noise is to come from. The
> diodes are just switches, the transformers
> have close to no loss and behave properly in power dividers, and even
> when the diodes are resistors for a moment,
> their noise is only half-thermal.

The diodes as not "just switches". The "switches" analogy is not 
helpful. It has an exponential function from voltage to current.

There is thermal noise because they have resistance.

There is flicker noise, as current flows through the semiconductor.

Cheers,
Maguns


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