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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 16:07:55 -0700
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On Mon, 27 May 2024 22:37:31 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>john larkin <jl@650pot.com> wrote:
>> 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?
>
>Normally unnecessary for a YTO, I think. 
>
>> 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.
>> 
>
>A well-degenerated BJT with a 2- or 3-pole lowpass on the base makes a deep
>sub-Poissonian current source. One of our laser drivers has a noise floor
>below -190 dBc/Hz at 400 mA, about 24 dB below shot noise. 
>
>You do have to handle the low baseband somehow, of course. For the laser
>driver it’s an op amp and voltage reference, and for the YTO it’s a PLL. 
>
>Cheers 
>
>Phil Hobbs 
>> 
>

Is the yig phase-locked to an XO? I guess that would make a nice
jump-tunable first-mixer oscillator. Something else would have to
sweep the IF.