[time-nuts] f-multipliers from VHF to 10 GHz

[jimlux]

On 5/14/20 5:58 PM, Gerhard Hoffmann wrote:
> I have a potential project in the electron spin spectroscopy sector and 
> I need
> one or two clean signal sources in the 10 GHz range. Phase noise at, 
> say, 50 Hz offset
> is important, but anything below 110 dBc  does not care.
> That probably calls for a multiplied crystal. These Hittite PLLs from AD 
> seem to be
> just not good enough, maybe they'd work if pushed, but no reserve left.
> Are there any known proven multipliers chains from VHF to 10 GHz?
> 

-110dBc @ 50 Hz offset at 10GHz? That's -170dBc @ 50Hz with a 10MHz ref. 
That's going to be a chore.. the Wenzel ULNs are -167dBc at 100Hz 
offset, and they're pretty good.

But, as far as your synthesis approach, maybe not the Hittite PLL, but 
what about using the Hittite dividers and/or VCOs, and a different kind 
of PLL. You're talking about the noise "inside the loop" so the not so 
wonderful GaAs ring oscillator far out noise isn't an issue.

We have used those VCOs and dividers for deep space transponder 
synthesizers, and that's a classic "gotta have really good close in 
noise" application.

Compared to a DRO, which has microphonics, limited tuning range, etc. 
they're a lot easier.

I notice that AD and TI both have a lot of new parts for <17GHz.  Sure, 
most are targeting wideband high data rate kinds of applications, but 
they might fill the need. What about the LMX2595 or LMX2594 - I've not 
used them, but they might be interesting.

The plot in the selection guide does show only -90dBc for the 2594 at 
8GHz, but I don't know if that's the bare VCO, or locked to something, 
and then you'd ask what it's locked to. The divider noise is something 
like -150dBc at 10GHz, so that's probably not your dominant source.