Discussion in 'CAD' started by yAro, Oct 16, 2006.

1. ### yAroGuest

Does anyone know if there any OrCad libraries
containing flat spiral RF inductors?
If no, then if I create an equivalent RLC circuit
how can I simulate the dependency
between inductance and frequency? Is it possible
at all in this application or should I
rather look for something else?
yaro

2. ### Jim ThompsonGuest

Make it up with a .SUBCKT declaration

Then, in Probe, look at the real and imaginary components of current
to derive inductance variation with frequency. (Create your own
MACRO)

...Jim Thompson

3. ### yAroGuest

I was hoping there may be some easy way, so even
someone who run an electronic Cad for
the firs time can do it. So far I learned only
some basics like building a circuit and running
PSpice
to get a graph showing current and voltage
behaviour of that circuit. I've got no idea where
to
look for .SUBCKT or Probe however, or how to
create macros in this application.
My guess is that the macro will have something to
do with using the formula for inductance where
L=2pi*f*X and X=Vo / Io as I found only
voltage, current and power markers in OrCad.
If it wouldn't be to much to ask for more detailed
explanation I would be
very grateful as the only reason why I get my
hands on OrCad is that I was hoping to find some
easy
way to simulate the relation between induction and
frequency for different numbers of turns of a flat
spiral coil to compare it with my measurements.
The program looks much more complex then I thought
and I never used any Cad applications before. I
thought it will rather allow me to draw the
component I
need, giving it all the characteristics I require
and then there will be an option to measure any
parameters
of that element that I need. Unfortunately it
isn't so.
J Celmer

4. ### LeonGuest

The Pulsonix software I use has interactive spiral design support:

Spirals using intelligent rules supported
Circular/square shape
Gap rules defined
Number of turns
Inner spiral width defined
Aspect ration for non-square shapes
Corner radius defined for circular shapes
Spirals can be made in Copper and non-electrical shapes
Spirals can be created and saved within the footprint definition

You need other software to simulate the inductor, though.

Leon

5. ### Charlie EdmondsonGuest

You are basically using the wrong software for the job. PSpice is a
general SPICE simulator, and CAN do RF simulation, but you have to do a
lot of the work yourself. What you are needing is an RF specific
simulator, that can take a spiral inductor definition and simulate it
for various characteristics. For that, you might be better served
looking at Microwave Office, or the Agilent tools. If you just need to
extract a generic spice model from your spiral, Ansoft has tools that
can do that.

But, if you are going to do spiral inductors and other RF design, you
are going to need CAD to get it right!

Charlie

6. ### yAroGuest

Thanks for the tip but I wan't be able to use it
for the simulation I'd like to perform
yaro

7. ### yAroGuest

You are basically using the wrong software for
Thanks Charlie. I checked MW Studio and from what
I found it is only suitable
for 2d objects and similarly like sonnet (fully 3d
tool) which I found fallowing the path
you suggested it doesn't use typical wires but
micro strips which I'm not too familiar with
and not sure if I can use them to simulate a macro
sized inductor with them. Also I'm not sure
what they mean by ports in both of the programs.
Honestly, I thought I could find something
more user friendly for old fashion electrical
engineers rather than computer experts.
Cheers
yaro

8. ### Charlie EdmondsonGuest

Welcome to the wonderful world of RF design. The rule is, THERE ARE NO
WIRES! Everything is a transmission line, and there are no 'just

Charlie

9. ### JoergGuest

Hello Charlie,
And in RF design there is no free lunch, usually

Anyway, Yaro, check this out:

10. ### Jim ThompsonGuest

On Fri, 20 Oct 2006 00:28:00 GMT, Joerg

[snip]

when ;-)

...Jim Thompson

Hello Jim,
Better?

12. ### Jim ThompsonGuest

Almost. Who's this "Jim" fellow you're saying "Hi" to ?

...Jim Thompson

13. ### JoergGuest

Ahm, some guy who know a thing or two about chips and red wine

So, is the "Hello" up top also not kosher on usenet? Sounds so
non-personal not to do that but if it is customary I guess I have to
drop it.

14. ### Jim ThompsonGuest

Look up how you reader can be configured. In Agent it's like this...

On %date%, %from% wrote:\n

which puts the previous poster's information just before the quoted
material.

You can easily add your "Hi" if you like... or other cutesy stuff...
see Spehro's posts for example ;-)

...Jim Thompson

15. ### JoergGuest

Hello Jim,

I'll try to figure it out. But I am using Mozilla which is a Windows app
without command line stuff and I am more of an assembler kind of guy...

16. ### Jim ThompsonGuest

Looks like you're getting close ;-)

All you need is the date attribution and you've got it... see the top
of this post.

Why is it that everyone wants to use a single tool to do all
functions?

Mozilla/Firefox is a browser, Agent is a newsreader, Eudora is an
E-mail client, etc.

...Jim Thompson

17. ### JoergGuest

It's so much easier. For the same reason I like my new CAD stuff. You
can scoot back and forth between layout and schematic without ever
leaving the program.

Maybe I should try Agent. But every time I switched web SW something
broke and took hours to fix.

I've used asitic in school some years back, and for free it's certainly
decent, although I'd also suggest the OP should check out Ansoft Designer SV
("student version") -- it's also free, and can analyze spiral inductors as
well as performing many other functions that your typical linear RF simulator
can; it also has a nice GUI (somewhat weird at times, but still easier than
direct netlist entry) and graphing abilities. One of the examples included is
a spiral example.

---Joel

I've often wondered how many people actually use (meaning "purchase!") that
extra option. I suppose that if you're designing a spiral inductor for, e.g.,
a switch-mode power supply then the actual inductor isn't that critical and
you could get away with analytical formulas, telling someone to layout a
spiral of such and such a size and number of turns, but for RF work you
necessarily end up with a layout as you perform simulations and tweak your
design anyway, which you'd just import into your PCB tool of choice.

Have you ever had a real board design where you used that feature, Leon?

---Joel

20. ### JoergGuest

Hello Joel,
It is amazing what kinds of design tools we have these days. In fact, I
didn't have to pull my old Bronstein/Semendjajew math dictionary off the
shelf for over a month now. However, when it comes to really intricate
stuff there is not much progress. When doing wave digital filters I
still have to resort to DOS tools. Oh well, the same goes for other
tasks, used grandpa's 70-year old planer to fix something on our deck
yesterday.

BTW, did you find other good candidates for the RF engineer opening?