Re: noise question

On 16/07/2024 7:52 pm, Gerhard Hoffmann wrote:

Am 16.07.24 um 05:29 schrieb Phil Hobbs:

Gerhard Hoffmann <dk4xp@arcor.de> wrote:

Am 15.07.24 um 20:04 schrieb john larkin:

On Mon, 15 Jul 2024 19:33:52 +0200, Jeroen Belleman
<jeroen@nospam.please> wrote:
>

On 7/15/24 18:09, john larkin wrote:

On Mon, 15 Jul 2024 17:35:08 +0200, Jeroen Belleman
<jeroen@nospam.please> wrote:
>

On 7/15/24 16:30, john larkin wrote:

<snip>

That assumes that oscillators are mostly linear, but they aren't.

They can be remarkably close to it, once the amplitude has settled down.
http://sophia-electronica.com/BillsBaxandall.html
uses an asymmetric current mirror to control the loop gain, and once you've got the amplitude where you want it - that at the right level of asymmetry - the current mirror is pretty linear.
If you use a AD734 four quadrant multiplier as your gain-setting device you can do even better, which is something I've only done in simulation,but should work in real life.

Switching on a really linear oscillator would imply an explosion
soon after power on.So there must be a large scale non-linearity
to limit the growth.

No. You just have to be able to control the gain around the loop to hold the amplitude of oscillation at a stable level. Obviously that gain has to be changed from time to time, but it doesn't have to changed all that much or all that fast.

 There are even proposals that say that there is an optimum point
in the cycle to inject all the feedback for best phase noise.

Seems implausible.

https://people.engr.tamu.edu/spalermo/ecen620/general_pn_theory_hajimiri_jssc_1998.pdf     >
(and books on it)
 Our ex-regular Kevin Aylward, WardenOf The King's Ale
<  https://www.kevinaylward.co.uk/    > has written fiercely
against that but people like Rubiola and U.L.Rohde seem to buy it.
 interesting:   <  https://rubiola.org/   >

--
Bill Sloman, Sydney
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