[time-nuts] Low noise frequency multiplication

Rick Karlquist richard at karlquist.com
Wed Feb 28 18:42:24 EST 2007


Stephan Sandenbergh wrote:
> How difficult is it to multiply a frequency standard from 10MHz to 100MHz?
>>
>
> The other day I stumbled across the following article on Wenzel's website:
>
>             http://www.wenzel.com/pdffiles/RFDesign2.pdf
>
>
>
> It describes a way in which an analogue odd-order frequency multiplier
> could
> be built cheaply with superior noise characteristics. This circuit that is
> described is really simple and quite ingenious. Unfortunately, I would
> like

I remember that article from when it was first published.  It is
quite clever, but has no special phase noise advantage compared
to any other passive limiter or passive frequency doubler based
on a full wave rectifier.

You need to be more specific about your multiplier requirements.
When I worked for Zeta Labs, we used to get vague RFQ's like this for
multipliers, and then have to develop a specification.  That is
almost more difficult that actually building the multiplier.
Are you after good Allan deviation or low phase noise?  Do you
care about phase noise floor?  How clean is the original oscillator?
In the HP 8662, they double a 10811 three times to 80 MHz and then
strip off the phase noise floor sidebands with a crystal filter.

Regarding X10:  I suggest you double to 20 MHz, take that as an
intermediate output, and then quadruple the 20 MHz to 80 MHz.
Then mix the 80 and 20 to get 100 MHz.  As far as heroically
multiplying directly by 5:  been there, done that, got the coffee
mug and T-shirt.  Don't do this at home kids.

Rick Karlquist N6RK




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