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.
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