[time-nuts] Designing and building an OCXO and GPSDO

[Luis Cupido]

Bruce, tks for your reply.

 > The latest spectrum analyser offerings from Agilent have similar phase
 > noise floors for both the millimeter wave and low frequency spectrum
 > analysers.

Yes, but kind of puzzles me a bit since I would
be expecting phase noises more than 10x worst on a
SA covering DC to 1GHz (+/-)
(since the LO for this is an YIG oscillator circa 3GHz locked to a 
reference)
comparing with an FFT analyzer that uses a few tens MHz sample rate.

Assuming similar 10MHz reference oscillator the SA
gets it multiplied by 300 while a low freq SA (preferably FFT)
gets it multiplied by 10 maximum.
How can they claim similar performance ?!
---

Ok on the rest, tks.


Luis Cupido.


Bruce Griffiths wrote:
> Luis
> 
> The latest spectrum analyser offerings from Agilent have similar phase 
> noise floors for both the millimeter wave and low frequency spectrum 
> analysers.
> However the low frequency analysers have a lower "flicker" noise corner.
> 
> The noise floor of a good double balanced mixer is still 30-40dB lower 
> than that a spectrum analyser.
> 
> Thus you are stuck with using a low bandwidth phase lock loop to get 
> down to the mixer noise floor.
> 
> Alternatively a dual (first conversion uses analog mixers, 2nd 
> conversion uses DSP techniques) conversion Costas receiver using 4 
> mixers and 4 ADCs should go down to -170dBc @ offsets of 100Hz or so 
> when correlation techniques are employed. Its a pity the TSC5120A doesnt 
> allow independent access to all 4 of its ADC inputs so a quad of 
> external mixers can be employed to extend the technique to the 
> millimeter wave region.
> 
> All you need is 4 high resolution ADCs and an offset generator or 2.
> A couple of high end sound cards may be suitable at least for testing 
> the concepts.
> 
> Bruce
> 
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