Well ~

You're almost right . . .

A typical RF Choke on a PCB is a certain length conductor (typically 1/4
wavelength), which is acting as an inductor, from one active part of an
RF circuit (typically the Collector of an RF Transistor) to another part
of the circuit, typically power (or sometimes ground), such that it is a
"short" at DC, and isolated (or open) at a given frequency. Thus one can
pass power thru the Choke to the Transistor, but it does not appear to
be a short at RF frequencies. There are other applications, but this is
probably the most common one you will find on a PCB, and is actually
quite common today.

Now - Go ask Protel how to make it . . .

No, don't give us your version (which we have already seen here in the
list), but go ask Protel how to make it.

JaMi Smith

-----Original Message-----
From: Abd ul-Rahman Lomax [mailto:[EMAIL PROTECTED]] 
Sent: Wednesday, February 20, 2002 1:44 PM
To: Protel EDA Forum
Cc: JaMi Smith; JaMi Smith
Subject: RF footprints

At 12:42 PM 2/20/2002 -0800, JaMi Smith wrote:

>(Go ahead, ask Protel what
>an RF Choke is, and how to make one in Protel).

Printed components tend to not have fixed sizes, unless they have fixed 
values or functions. If one wanted to make an RF choke footprint, one
have to have a separate footprint for each value, with variations on
for various choke parameters.

Instead, one would provide a wizard for generating such parts; feed the 
wizard the PCB parameters -- which is already in the PCB file --, type
pattern, desired parameters, and the wizard would attempt to create a 
pattern that satisfied the conditions. I have in the past been given 
dimensions for creating series of certain narrowly defined parts, the 
dimensions came from work with a field solver or other similar programs.

(I'm not an RF engineer, but I work closely with one.)

All this would fit very nicely into the Protel mission, but it is not a 
simple piece of work.

Abdulrahman Lomax
Easthampton, Massachusetts USA

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