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NNTP-Posting-Date: Mon, 27 May 2024 15:25:40 +0000
From: john larkin <jl@650pot.com>
Newsgroups: sci.electronics.design
Subject: Re: Small magnetic tunable filter for 6G and beyond
Date: Mon, 27 May 2024 08:25:40 -0700
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On Mon, 27 May 2024 12:58:08 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>Jeroen Belleman <jeroen@nospam.please> wrote:
>> On 5/27/24 07:08, Jan Panteltje wrote:
>>> To 6G and beyond: Engineers unlock the next generation of wireless communications:
>>> https://www.sciencedaily.com/releases/2024/05/240524114938.htm
>>> Source:
>>> University of Pennsylvania School of Engineering and Applied Science
>>> Summary:
>>> Engineers have developed a new tool that could unlock 6G and the next
>>> generation of wireless networks: an adjustable filter that can
>>> successfully prevent interference in high-frequency bands of the electromagnetic spectrum.
>>> partial quote:
>>> What makes the filter adjustable is a unique material, "yttrium iron garnet" (YIG),
>>> a blend of yttrium, a rare earth metal, along with iron and oxygen.
>>> "What's special about YIG is that it propagates a magnetic spin wave," says Olsson,
>>> referring to the type of wave created in magnetic materials when
>>> electrons spin in a synchronized fashion.
>>> When exposed to a magnetic field, the magnetic spin wave generated by
>>> YIG changes frequency.
>>> "By adjusting the magnetic field," says Xingyu Du, a doctoral student in
>>> Olsson's lab and the first author of the paper,
>>> "the YIG filter achieves continuous frequency tuning across an extremely
>>> broad frequency band."
>>> As a result, the new filter can be tuned to any frequency between 3.4 GHz and 11.1 GHz,
>>> which covers much of the new territory the FCC has opened up in the FR3 band.
>>> 
>> 
>> YIG filter and resonators have always been a bit exotic. Maybe this
>> will make them common-place. And more compact, hopefully! The YIG
>> was tiny, sure, but the magnet wasn't.
>> 
>> Jeroen Belleman
>> 
>
>YIG-tuned VFOs are the champs for low close-in phase noise. My HP 8566B’s
>noise floor at 1kHz is a good 30 dB better than any SDR-style analyzer. 
>
>If they manage to get them down to Digikey-level practicality without
>screwing that up, it would be huge. 
>
>I wonder if you could use a mag amp sort of structure, with a rare earth
>magnet biasing some cleverly designed bits of saturable ferrite, plus some
>small coils changing the effective gap in the magnetic circuit. 
>
>Fun to think about. 
>
>Cheers 
>
>Phil Hobbs 

How can one keep a magnetic field stable to parts per billion?

Seems like ambient 60 Hz fields and temperature changes and tiny
noises in the coil current would dominate. It's hard to regulate a
current to parts per million.

Qs are low too.

Does your HP have a big ovenized mu-metal box inside?