[time-nuts] Ultra low phase noise floor measurement system for RF devices.

[Dr Bruce Griffiths]

SAIDJACK at aol.com wrote:
>  
> In a message dated 3/30/2007 16:02:15 Pacific Daylight Time,  
> bruce.griffiths at xtra.co.nz writes:
>
> It does  in fact measure below the thermal noise floor.
> This is not too difficult as  it uses a crosscorrelation technique.
>
> Bruce
>
>
>
> Hi Bruce,
>  
> interesting how microphonic effects would affect the results.
>  
> I see my instrumentation jumping by several 1E-12 units everytime I walk  
> into the lab since my benches are not shock insulated.
>  
> At -200dBc (we have to think about that number for a while!!) - that's  
> counting single electrons every couple of seconds I would think...
>  
> bye,
> Said
>
>
>
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Said

Actually I should have said -200dBc/Hz.
With a +13dBm carrier this corresponds to a noise voltage of 100pV/rtHz 
across a 50 ohm resistor or a noise current of 2pA/rtHz  flowing through it.
Even with a 1Hz noise bandwidth thats an rms fluctuation of about 
12,500,000 electrons. You have to get down to noise currents of  around 
1attoAmpere/rtHz before you start "counting" individual electrons.

Yes vibration isolation, is essential which is why their prototype was 
built on a vibration isolated optical table.

Bruce