In message <004a01c0f421$3302e620$02a2fea9@mike>, Mike Reagan
<[EMAIL PROTECTED]> writes
>Hello All.
>I wanted to throw in my two cents:
>While a Spiraled trace to simulate an inductor might be a desirable
>accomplishment, I try to convince engineers to stay away from this type of
>design. I call it Voodoo design. Unless the trace is designed first by a
>very powerful tool that takes into account three dimensional design, the
>probability of obtaining a coil with any good characteristics is slim and
>inconsistent. For edge to edge coupling to be effective coupling the traces
>would have to be closer than 7 mils apart. Then there is "Q" factor for
>this inductor, meaning it will be a very poor Quality inductor. I
>personally think and would suggest finding a real component to design in.
>Your design will be more reproducible and consistent from board to board,
>because of a number of problems inherent to varied inconsistencies of a
>fibers in any board. There are a whole lot of reasons why I would stay
>away from voodoo design. Sorry Bill, I don't mean to insult you, are the
>only TOP GUN registered on this list. But I wouldn't attempt it unless I
>could fully simulate it at my desired frequency, with prepreg thickness,
>with known prepreg material, fiber density, dielectric constant, gnd plane
>underneath, relative humidity, and it goes on.
>
>I will wait for Brad V's Comments on this because he had mentioned his
>company simulates some of this stuff, right?
>
Mike,
It used to be an iterative process a while back, but newer design
packages allow spiral inductors to be simulated before layout.
I agree with you not to use printed inductors unless you can simulate
them reasonably well.
I use Genesys for some RF design which is a relatively "low-end"
package. It has a spiral inductor model which can be laid down as copper
and run through the EM simulator for a reasonably accurate simulation.
The Gerber files for this pattern can be exported and I've got it into
Camtastic easily enough.
On a general note, many PCB packages do not handle RF components well. A
recent exposure to Veribest has shown that top-end stuff is just as bad,
though I note that some new packages are coming along to specifically
integrate (or at least work with) some RF simulation tools. I trust that
these handle, for example, Microstrip structures a little better.
Regards
--
David Want
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