Hej,
On Monday, 29 November 2021 04:29:58 CET Matt Huszagh wrote:
> I've got a 10 MHz distribution amplifier and am considering purchasing a
> 5 MHz reference. Most (not all) of my equipment accepts a 5 MHz
> reference, but I'd like to be able to use the existing distribution
> amplifier I have if possible. Therefore, I'm considering ways I might
> generate a low-noise 10 MHz signal from the 5 MHz reference.
>
> An obvious way is to use a doubler. However, as I understand it, even an
> ideal doubler will add 20log(2)=6 dB of phase noise to the 10 MHz
> signal.
Yes, this is a fundamental physical property which cannot be avoided.
You can see it that way: If there is a given fluctuating time delay in your
otherwise perfect 5 MHz signal, the amount of phase shift this time
fluctuation corresponds to in a 10 MHz signal is simply twice as big as in the
5 MHz signal, simply because the phase evolves twice as fast at 10 MHz.
This factor of two makes up the 6dB in noise power.
If you divide the 6 dB noisier 10 MHz signal down again, (neglecting
additional technical noise), you get the original performance of your 5 MHz
signal back.
Cheers,
Jürgen
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