[time-nuts] Advantages of differential oscillator structures?

[Bob Camp]

Hi

I think you'll find that the low current amps in their schematic have pretty large 1/f noise. 

Bob

On Aug 10, 2013, at 11:04 AM, Magnus Danielson <magnus at rubidium.dyndns.org> wrote:

> 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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