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TUTORIAL - Example 1, Using Femm to Calculate Component Values of Simple Microstrip to use in LTspice/PSpice

I offer to share with you a TUTORIAL but don't know how to get it into your hands.

The TUTORIAL is about 15kB, zipped, and describes the step-by-step process of using FREE femm 4.2 to analyze a simple PCB structure to calculate values to then use in circuit simulation, LTspice/PSpice. The sequence can be modified for use in analyzing really complex structures, structures where there are NO formulas. [I know there are many formulas and online calculators for 'normal' structures that can provide similar values, BUT they deprive you of gaining any understanding.]

The simple structure in this example is a 50 ohm microstrip implemented using 1 oz copper on a four layer 1 inch wide 5 inch long FR4 PCB operating at 10MHz. The trace is 16 mils wide, copper 1.4 mils thick, and dielectric separations of 9 mils each with the overall PCB thickness approx 32 mils. The stack up is: Layer 1 Trace Layer 2 GND Layer 3 Vcc Layer 4 Trace

An exmaple, of gaining insight:

If the microstrip uses only the top two layers, evrything is 'normal' and as expected. Current flows into the SIGANL trace and is RETURNed through the GND plane. Of course no one would do that, you would always keep the next layer, Vcc, and use it as a pseudo-ground plane.

BUT! Now something very interesting happens. The RETURN current splits between GND plane and Vcc plane, where the current in GND plane is in the correct direction, but slightly MORE than what you put intn SIGNAL! and there is a slight bit of that 'extra' current flowing in the Vcc plane, BUT IN THE SAME DIRECTION AS THE SIGNAL??!!

No book formula I've ever found will show you this, so there is 'education' in getting down into details.

As I said, this is a step-by-step tutorial, with descriptions, explanations, and dedicated femm drawings for each step culminating in LTspice schematics of the final model. Hopefully, educational/useful for someone out there.

Regards, Robert

Reply to
RobertMacy
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This sounds very interesting and I guess a lot of good karma is headed your way for collaborating in this way

How do I get the 15kB file?

Thanks

Klaus

Reply to
Klaus Kragelund

How about putting it on Dropbox or someplace like that?

ABSE would work for many of us as well.

Cheers

Phil Hobbs

Reply to
Phil Hobbs

On a sunny day (Tue, 05 May 2015 03:36:33 -0700) it happened RobertMacy wrote in :

Ms. Maple?

Reply to
Jan Panteltje

Dropbox? Or send me an email attachment and I'll stick it up in my dropbox.

@teachspin or ggherold at sign gmail

George H.

Reply to
George Herold

Hi, Klaus,

If your email address works, I sent it.

Reply to
RobertMacy

Does nobody read?! I constantly complain about the 'toxicity' of those websites, Dropbox, etc. Dropbox and all those 'free' websites sell something to somebody ...else, Their customers are NOT the users. Those websites start 'poking' around inside our PC's, causing hangs, and worst of all, total crashes that require Power OFF reboots! And the times I sit and wait and wait and they didn't crash us, they didn't even give me access to what somebody dropped there. So, NO I now NEVER you those 'free' websites.

Reply to
RobertMacy

Send it to me and I'll put it on the S.E.D/Schematics Page of my website. No scripts, no nutting, just look/see ;-) ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142     Skype: skypeanalog  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

Just sent to your 'teachspin' address: you did NOT set me up to accept any .zip files, but at least YOUR server has the courtesy to tell someone it threw away the email.

got this error: Technical details of permanent failure: Google tried to deliver your message, but it was rejected by the server for the recipient domain teachspin.com by mx0.managemyspam.com. [72.88.83.109].

The error that the other server returned was:

552 Filename not allowed: 'TUTORIAL_StepByStep.zip' (#5.7.1)

Will try again to ggherold at sign gmail dot sign com

Reply to
RobertMacy

Will do, it's small at only 15kB

Reply to
RobertMacy

ARRRGGGG!!!!

I sent the WRONG file to any of you!

should have been the TUTORIAL_Example01.zip

Throw away the TUTORIAL_StepByStep.zip !!!

I'll go back and do again!

...sigh

Regards to all, Robert

Reply to
RobertMacy

Fortunately I took me a while, so hopefully this is the correct file.

formatting link

George H.

Reply to
George Herold

I'm not aware of any problems with Dropbox, except that it seems to slow down my computers a bit, which is reasonable since it's doing a lot of file transfers and checks and stuff. I no longer need to carry memory sticks around, and have access to my stuff on my 4 working computers scattered around the state. I think their biz model is to give away a couple of gigabtyes of storage, get people hooked, and get a few percent of their users (like me) to pay for more.

Dropbox is wonderful. The future is access to your stuff anywhere, anytime, on any device.

The automation of our cabin in the mountains (remote cam and heating control) is also through shared files on Dropbox.

--

John Larkin         Highland Technology, Inc 
picosecond timing   laser drivers and controllers 

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com
Reply to
John Larkin

Well, you don't have to install the software. ABSE, then.

Cheers

Phil Hobbs

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

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net
Reply to
Phil Hobbs

On a sunny day (Tue, 05 May 2015 08:05:52 -0700) it happened RobertMacy wrote in :

Did you see a shrink for paranoia?

Reply to
Jan Panteltje

On a sunny day (Tue, 05 May 2015 09:17:38 -0700) it happened John Larkin wrote in :

As I just demonstrated again, running your own server is no problem at all, so you do not need dropping boxes.

Reply to
Jan Panteltje

Dropbox runs a nice server farm (Amazon's actually), all backed up and stuff. All my app has to do is write a file, and it's automagically replicated on all my PCs.

One cool thing is that if Dropbox dropped off the face of the planet, all my files would still be there, on all my PCs.

I work at work, at home, in the cabin, and sometimes on the road. I can do anything anywhere with minimal overhead.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com
Reply to
John Larkin

Yes, persistent Internet threats (black hat hackers)love dropbox. It puts a big security hole in your system.

Reply to
David Eather

Now posted on the Simulations Tools & Macros Page of my website. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
       Statistics means never having to say you are certain
Reply to
Jim Thompson

And if any one of those computers appears to its local Dropbox install to have deleted one of those files, poooff, it's gone from all of them.

I use a Git repository, and push and pull updates manually. Each repository contains the entire history.

Robert: If you want to use Dropbox but don't want their drivers and software running on your computer, you can still use the web-only service.

Clifford Heath.

Reply to
Clifford Heath

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