Ebit 
Post subject: Ansoft Design Users Unite: Q on Modeling a Magnetic Dipole
Posted: Fri Aug 05, 2005 10:41 pm


Joined: Fri Aug 05, 2005 8:25 pm
Posts: 2 Location: Santa Barbara

Hello,
I have just begun interfacing
with Ansoft's Designer (SV). I am trying to
model a magnetic dipole in free space, operating
at 10GHz and extract the radiation resistance.
This is well known theory: Rrad=197*((a*omega)/c)^4
[Ohms] where: a=the radius of the loop
omega = 2*pi*f c=the speed of light For
a<<lambda
Here is what I have thus
far:
Two layers of air dielectric both
of thickness = lambda/2 =15mm A lossless
conductor for my signal layer. The signal layer
is sandwiched between the two dielectrics.
Defined "Drawing extent" (Layout>>Settings)
such that each edge (Left, right, top, bottom)
are 2*lambda from the center where the dipole
is located. I have done this too provide adequate
space for the farfield approximation to be
accurate, but I would like to know if this is
necessary. Any thoughts?
The geometry:
I have constructed a square loop (at this level
of approximation (a<<lambda) it shouldn’t
matter if the geometry is square or circular)
by making a square cell 60x60 microns^2. I copied
and pasted this cell four times then assembled
to form a square horseshoe. I closed the loop
with two rectangles 60x90microns^2. This leaves
a void of 60x60 microns^2 in the middle.
I would like to have one port located between
the two rectangles (centrally located rather
than on a corner) to provide a voltage potential
and setup circulating currents. Is there a better
design choice? Any suggestions?
Results
(so far): I tried the single edge port (which
then defaulted to a gap source) and Ansoft gave
me the following error: “Edge port is not
represented in the mesh: port 1”
Then
I tried separating the loop just slightly and
defined two ports one on each edge (now facing
each other) so the geometry looks like square
“C”. No errors. However, the currents are virtually
nonexistent.
I would appreciate any
suggestions:
Meshing: Fixed (with or
with out edge mesh) vs. Adaptive Port placement
ideas etc…


Posted 11/12/2012
