[time-nuts] Re: Working on a low-phase-noise frequency multiplier

[Ed Marciniak]

For certain use cases, sometimes a mixer is used to compare the two and steer the tuning element. This avoids the divider element altogether. I'd expect you'd want buffer amplifiers that have high isolation to ensure one oscillator doesn't pull the other. The right mix might also be something in between for simplicity, like an amplifier, a diode doubler, an amplifier, and a mixer to compare 2 MHz to 10MHz or 5MHz from the 2.5x2 to the 10MHz, and in either case using an op-amp to drive the 10 MHz oscillator's tuning element.

It would also be fair to consider what quality 10MHz oscillator is required so that with appropriate low pass filtering its performance is maximized, and better that simply cascading doublers.

-----Original Message-----
From: Bill Ezell via time-nuts <time-nuts at lists.febo.com> 
Sent: Friday, August 25, 2023 12:40 PM
To: time-nuts at lists.febo.com
Cc: Bill Ezell <wje at quackers.net>
Subject: [time-nuts] Working on a low-phase-noise frequency multiplier

I have some old frequency standards that provide 1, 2.5, or 5 Mhz outputs, not great for comparing against modern 10Mhz standards.

I could do a divider, pretty easy, but only useful for doing analysis. 
Better to have 10Mhz output.

So, I'm thinking a multiplier. There are many versions, from simple diode ones and up.

It seems that doing an integer-N PLL with a VCXO would be the way to go. 
The capture range can be quite narrow since the input will be something that's within a 1 Hz range and a long loop constant might be good. Plus, with a good-quality VCXO, I would expect the noise figure to match the VCXO's pretty closely.

Any comments before I wander off into la-la land? BTW, Analog Devices has some good PLL design tools.

So, what sparked this? I bought one of the Sulters that was mentioned a while back, 2.5Mcycles (gotta be historically accurate). I also have an equally-ancient Vectron double-oven std that, last I tested it, was down in the e-11 or better range. I also got a TinyVNA which is now a TinyPFA, and it can only deal with equal freq inputs. I want to also compare that against my HP 5370 and 53310. You can see the slippery slope.

Thanks, Bill

--
Bill Ezell
I happen to know that this is the Lupin Express.
_______________________________________________
time-nuts mailing list -- time-nuts at lists.febo.com To unsubscribe send an email to time-nuts-leave at lists.febo.com