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From: Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>
Newsgroups: sci.electronics.design
Subject: Re: BAW
Date: Sun, 26 Jan 2025 03:11:42 -0000 (UTC)
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john larkin <JL@gct.com> wrote:
> On Sat, 25 Jan 2025 19:36:19 +0000, Cursitor Doom <cd@notformail.com>
> wrote:
> 
>> On Sat, 25 Jan 2025 09:05:42 -0800, john larkin <JL@gct.com> wrote:
>> 
>>> On Sat, 25 Jan 2025 13:55:05 +0000, Cursitor Doom <cd@notformail.com>
>>> wrote:
>>> 
>>>> On Fri, 24 Jan 2025 17:46:24 -0800, john larkin <JL@gct.com> wrote:
>>>> 
>>>>> On Sat, 25 Jan 2025 00:41:39 +0000, Cursitor Doom <cd@notformail.com>
>>>>> wrote:
>>>>> 
>>>>>> On Wed, 22 Jan 2025 17:09:29 -0800, john larkin <jl@glen--canyon.com>
>>>>>> wrote:
>>>>>> 
>>>>>>> On Thu, 23 Jan 2025 00:55:25 +0000, Cursitor Doom <cd@notformail.com>
>>>>>>> wrote:
>>>>>>> 
>>>>>>>> On Wed, 22 Jan 2025 10:55:39 -0800, john larkin <jl@glen--canyon.com>
>>>>>>>> wrote:
>>>>>>>> 
>>>>>>>>> On Wed, 22 Jan 2025 18:07:06 +0000, Cursitor Doom <cd@notformail.com>
>>>>>>>>> wrote:
>>>>>>>>> 
>>>>>>>>>> On Mon, 20 Jan 2025 16:26:10 -0800, john larkin <JL@gct.com> wrote:
>>>>>>>>>> 
>>>>>>>>>>> On Mon, 20 Jan 2025 19:52:03 -0000 (UTC), Phil Hobbs
>>>>>>>>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>>>>>>>>>>> 
>>>>>>>>>>>> john larkin <jl@glen--canyon.com> wrote:
>>>>>>>>>>>>> https://www.ti.com/product/CDC6C
>>>>>>>>>>>>> 
>>>>>>>>>>>>> These are like 35 cents at 1K.
>>>>>>>>>>>>> 
>>>>>>>>>>>>> 
>>>>>>>>>>>> 
>>>>>>>>>>>> Of course a crystal oscillator is a BAW device too. ;)
>>>>>>>>>>>> 
>>>>>>>>>>>> Cheers 
>>>>>>>>>>>> 
>>>>>>>>>>>> Phil Hobbs 
>>>>>>>>>>> 
>>>>>>>>>>> Don't get technical with me!
>>>>>>>>>>> 
>>>>>>>>>>> I wonder if it's all silicon, a sort of bulk MEMS thing. The price is
>>>>>>>>>>> absurd. I guess every one has to be trimmed to frequency.
>>>>>>>>>> 
>>>>>>>>>> Phil's pretty good in that regard. There are some people who see
>>>>>>>>>> everything in terms of equations and use higher mathematics to explain
>>>>>>>>>> their function. A xtal oscillator would provide a very simple example
>>>>>>>>>> for such persons to exhibit this (most unfortunate) character trait.
>>>>>>>>> 
>>>>>>>>> Phil is one of those people who can see equations in motion. I can't.
>>>>>>>>> I operate on instinct and simulation.
>>>>>>>>> 
>>>>>>>>> We have brainstormed on some pretty important projects and generated
>>>>>>>>> some ideas that influence most everyone here. The skills are
>>>>>>>>> complementary.
>>>>>>>>> 
>>>>>>>>> His book is good to have if you design electro-optics or low-level
>>>>>>>>> analog stuff.
>>>>>>>>> 
>>>>>>>>> https://www.amazon.com/Building-Electro-Optical-Systems-Making-Applied/dp/1119438977/ref=sr_1_fkmr0_1?crid=3M9PG1T68443R&dib=eyJ2IjoiMSJ9.xIlGO_AWviZZRYMlHFKJuNzKnLc8MDBpUjgE7RsYsDk.WiFCuc8GjBlGtPimMCFx0kOu5NieBv0TzXDNCokyLQM&dib_tag=se&keywords=phil+hobbs+optics&qid=1737571796&s=books&sprefix=phil+hobbs+optics%2Cstripbooks%2C138&sr=1-1-fkmr0
>>>>>>>>> 
>>>>>>>>> Be cautioned that there are equations.
>>>>>>>> 
>>>>>>>> Equations are fine (unavoidable anyway) in this science. But it's not
>>>>>>>> helpful in the first instance to gain an intuitive idea of how
>>>>>>>> something works - unless you're one of the people I mentioned above.
>>>>>>>> This is my main issue with Tom Lee's otherwise superb book, 'Planar
>>>>>>>> Microwave Engineering' where he typically launches into higher
>>>>>>>> mathematics almost from the get-go.
>>>>>>> 
>>>>>>> I have that book. It's mostly useless. One equation will be a full
>>>>>>> page of fine print, and then the next page turns out to be one term of
>>>>>>> that equation.
>>>>>> 
>>>>>> 
>>>>>> Indeed. Not only that, but the mathematics is unfamiliar. I know most
>>>>>> of the equations for transmission line theory by sight, but the ones
>>>>>> Tom cites are completely different and tend to use a lot of Greek
>>>>>> letters which relate to physical constants I've never even heard of.
>>>>>> On the other hand, where he doesn't use unfamiliar mathematics,
>>>>>> there's a *lot* in there I haven't seen any any other RF books which I
>>>>>> find really interesting.
>>>>> 
>>>>> It's easier to design with a geometry for which there are good
>>>>> calculator programs.
>>>>> 
>>>>> We have used ATLC to do e/m simulations of transmission line cases.
>>>>> 
>>>>> https://www.dropbox.com/scl/fi/6kdejmbybk4u5mq1xjait/Edge_alone_4.jpg?rlkey=volom4afazo44o6cpedgl89ge&raw=1
>>>>> 
>>>>> https://www.dropbox.com/scl/fi/82ysq5m13br8ahubdi4z7/Rob1.jpg?rlkey=4bnm3uu5otfolka9gqsov5tel&raw=1
>>>>> 
>>>>> https://www.dropbox.com/scl/fi/ogfqs1m93mf1uw80hwkpi/Rob_51_ohms.jpg?rlkey=u4q3fumbzwmpojck5ih88c45q&raw=1
>>>>> 
>>>>> That one butchers a multilayer PCB stack to get a good match with a
>>>>> cheap edge-launch SMA connector.
>>>>> 
>>>>> https://www.dropbox.com/scl/fi/n7hlatrxdoiywfkvebqj9/DSC01527.JPG?rlkey=hycib2nrk4zv662mu5vndy23g&raw=1
>>>>> 
>>>> 
>>>> I had to google ATLC simulator as I've not heard of it before. Anyway,
>>>> these plots are all very interesting, but you have no way of verifying
>>>> their accuracy AFAICS.
>>>> You mentioned a while ago you had a good source for cheap but
>>>> reasonable quality edge connectors (Aliexpress?) Can you post a link
>>>> to them please?
>>> 
>>> ATLC2 is a bit easier to drive.
>>> 
>>> The way to verify a sim is to make a board and TDR it. They are
>>> usually close.
>>> 
>>> The one in the pic above is from Shining Star.
>>> 
>>> SHINING STAR        19521000
>>> 
>>> We use 
>>> 
>>> SHINING STAR        24521116
>>> 
>>> too, a bit longer part. Both about $1.90.
>>> 
>>> 
>>> I've bought a bunch of similar ones from Amazon and they have been
>>> great. But it's our general policy to not use Amazon parts in
>>> production.
>>> 
>>> Here's a 4-layer proto board that let us TDR the connectors and the
>>> relay.
>>> 
>>> https://www.dropbox.com/scl/fi/bvcnqnvb4euc7pqw7wzab/DSC06884.JPG?rlkey=q1op81z1bumkfxoq8d5mtzi91&raw=1
>>> 
>> 
>> Forgot to mention (and sorry if I've asked you this before but you
>> have to allow me some extra forbearance on account of my age) - what
>> do you use for your TDR?
> 
> I have an ancient Tek 11802 with an SD24 TDR plugin.
> 
> 

My SD-24s have been dropping like flies lately—I have four that show
“Illegal channel number “and only one that still works. 

Cheers 

Phil Hobbs 

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