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From: Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>
Newsgroups: sci.electronics.design
Subject: Re: Small magnetic tunable filter for 6G and beyond
Date: Mon, 27 May 2024 20:54:59 -0400
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On 2024-05-27 19:07, john larkin wrote:
> 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.

> 
> 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.
> 

The 8566B has a complicated frequency plan that I've never gone into in 
full detail.  Sure works though!

Cheers

Phil Hobbs

-- 
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com