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From: Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>
Newsgroups: sci.electronics.design
Subject: Re: Yttrium iron garnet
Date: Thu, 30 May 2024 21:46:20 -0000 (UTC)
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john larkin <jl@650pot.com> wrote:
> On Thu, 30 May 2024 11:03:19 GMT, Glen Walpert <nospam@null.void>
> wrote:
> 
>> On Thu, 30 May 2024 09:14:58 -0000 (UTC), Cursitor Doom wrote:
>> 
>>> On Thu, 30 May 2024 15:45:21 +1000, Bill Sloman wrote:
>>> 
>>>> On 30/05/2024 3:37 am, john larkin wrote:
>>>>> On Wed, 29 May 2024 17:12:21 -0000 (UTC), Cursitor Doom
>>>>> <cd999666@notformail.com> wrote:
>>>>> 
>>>>>> On Wed, 29 May 2024 13:52:34 +1000, Bill Sloman wrote:
>>>>>> 
>>>>>>> Yttrium iron garnet tuned oscillators were around back then, but
>>>>>>> their 2GHz to 8GHz range was too high for me to count with the
>>>>>>> integrated circuits around then - we had to go the Gigabit Logic's
>>>>>>> GaAs parts to get to 800MHz, and that became the unique selling
>>>>>>> point of the system.
>>>>>> 
>>>>>> YIG oscillators were quite the thing back in the day, but I'm
>>>>>> guessing they've been completely superseded by now to get to ever
>>>>>> higher frequencies. Seems we've gone from -
>>>> 
>>>> This misses Jan Panteltje's thread "Small magnetic tunable filter for
>>>> 6G and beyond" which is about Yig being used today.
>>> 
>>> That article makes it seem like YIG is some revolutionary, new, emerging
>>> technology!
>> 
>> Use of YIG filters as a replacement for varactor tuning could turn out to 
>> be significant.  2022 Microwave Journal article:
>> 
>> <https://www.microwavejournal.com/articles/37980-reinventing-yig-
>> technology-for-microwave-filter-applications>
> 
> The VIDA oscillators still look like giant expensive power hogs. They
> don't specify modulation bandwidth on the data sheets that I see, but
> it must be terrible.
> 
> One can't modulate a hundreds-of-mA electromagnet very fast.
> 
> An LC osc with a varicap is a more sensible VCO. Narrowband, one can
> varicap a coaxial ceramic resonator, or a PCB ring oscillator, or
> something. Cheap and fast.

And far, far noisier than the best YIGs. 

> 
> Of course, it's inherently difficult to modulate a high-Q resonator
> fast, even without an electromagnet in the way.

It isn’t, actually, at least over a restricted range. If the resonator
obeys a differential equation, you can modulate its resonance much faster
than f_0/Q by changing L or C. 

Resonators with significant time delay, such as a long piece of coax,
aren’t as friendly that way. 

Cheers 

Phil Hobbs 

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