IMPROVING THE FREQUENCY STABILITY OF MICROWAVE OSCILLATORS BY
UTILIZING THE TEMPERATURE COMPENSATED DIFFERENCE FREQUENCY OF A
DUAL-MODE SAPPHIRE LOADED CAVITY RESONATOR
https://images.search.yahoo.com/yhs/search;_ylt=AwrUiqr58Fpe2kYAigIPxQt.;_ylu=X3oDMTByNWU4cGh1BGNvbG8DZ3ExBHBvcwMxBHZ0aWQDBHNlYwNzYw--?p=poseidon+scientific+whispering+gallery+oscillators&fr=yhs-dcola-001&hspart=dcola&hsimp=yhs-001#id=0&iurl=https%3A%2F%2Fwww.researchgate.net%2Fprofile%2FMichael_Tobar%2Fpublication%2F242255140%2Ffigure%2Ffig1%2FAS%3A669508037509121%401536634563175%2FThe-frequency-of-the-WGE-11-0-0-mode-and-the-difference-between-the-WGE-11-0-0-and-WGH_Q320.jpg&action=click
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Alex
On 2/29/2020 2:57 PM, Richard (Rick) Karlquist wrote:
On 2/29/2020 1:58 PM, Attila Kinali wrote:
Different concept. Quartz oscillators are mechanical resonators.
Cryogenic sapphire oscillators are electro-magnetic resonators.
The problem with those is, that they are large and need liquid He
for cooling. Not only is He expensive, but it also needs a cryostat
that will mechanically shake the CSO. But they get down to a few parts
in 10^-15 between 1s and ~1000s, I've even seen papers with a few parts
in 10^-16 in the same range(e.g. [1]) . There have been attempts to get
them to liquid nitrogen temperatures [2]. But they only got down to
1e-13
(i.e. where good crystal oscillators are). And not much happend since,
beside an attempt to get them working at room temperature [3]
Agilent (now Keysight) attempted for years to put a whispering
gallery oscillator in an instrument. It wasn't cyrogenic.
They actually heated/cooled it to lock it to a 10811. The real thing
that stymied them was microphonics. I retired in 2014 and don't know
whatever became of this effort. The two biggest experts on WGO's went
with Agilent during the Keysight spinoff, which might have finally
killed it completely. A cryogenic WGO would face the same microphonic
issues.
Rick N6RK
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