[time-nuts] Advantages of differential oscillator structures?

Magnus Danielson magnus at rubidium.dyndns.org
Sat Aug 10 11:04:06 EDT 2013


On 08/10/2013 12:10 PM, Attila Kinali wrote:
> On Sat, 10 Aug 2013 02:39:35 -0700
> wb6bnq <wb6bnq at cox.net> wrote:
>
>> I gather you did not fully read the paper ?
> I did, but...
>
>> This paper presents a circuit topography that allows the low current 
>> operation at a high frequency (12.8 MHz) thus reducing complexity.  This 
>> in turn allows the design and manufacture of a radio system using one 
>> crystal oscillator at a frequency of 12.8 MHz (example in the paper) 
>> with the low power advantage that previously required two oscillators.
> That's one advantage, and not a small one, but differential oscillators
> have been in use earlier and even in places where power consumption did
> not matter much. It pops up in crystal oscillator designs now and then
> but without any mention why this architecture was choosen. So i started
> to wonder whether there was any additional advantage than just lower
> power consumption and being able to work with less headroom, like better
> phase noise or better long term stability or less harmonics.
Well, at least from this paper they have not analyzed that. Here they
only use it for it's benefits in power, which is obvious from the Abstract.

If you wish to know other benefits, they need to be analyzed separately,
which by itself might prove an interesting paper. Reducing current drawn
should be interesting, as this should reduce 1/f noise in the feedback
amp, which should make the 1/f^3 noise lower significantly, which should
be beneficial for the stability of the oscillator in noise terms,
however it might not be beneficial for the oscillator in systematic
frequency drift terms. As always, it's a balance thing.

It should not be too hard to build it, try it, measure it and learn from
it. Sounds like fun!

Cheers,
Magnus


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