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radiation boundary - RF Cafe Forums
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| Karthik
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Post subject: radiation boundary
Posted: Sat Jan 07, 2006 10:48 am
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Hi,
Can anyone suggest the optimum size
of the radiation boundary box for an antenna in
HFSS? If I use the default radiation box, HFSS places
the box at the edge of the board. In one of the
manuals for an earlier version of HFSS, they have
used a box that is quarter-wavelength bigger than
the board on 3 sides for a patch antenna, while
in the manual for version 9, the box is a lot closer
to the patch.
As expected, my results vary
depending on the size of the radiation boundary
box. Can anyone help me on this?
Karthik.
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AP |
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Post subject:
Posted: Mon Jan 09, 2006 10:53 am
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I have a feeling that a quarter-wave is pretty close...
for microstrip circuits I try and keep the airbox
10x the substrate thickness - i.e. 2.5 mm for a
10 mil alumina substrate... so while I'm not sure
where the optimum placement is, you could also try
and keep moving the box further and further away
from your antenna until the results don't change
very much.
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Karthik |
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Post subject:
Posted: Mon Jan 09, 2006 12:52 pm
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I have a dipole in front of a ground plane. If I
take the 'substrate thickness' to be the total depth
of the arrangement - i.e, pcb thickness plus the
distance between the dipole and the ground plane
(this total thickness works out to roughly 20mm),
my air box is still 8x this size. However, my results
still vary. The gain varies by about half a dB,
and as long as the box is symmetrically big on all
sides, the pattern doesnt change. The input impedance
varies quite a bit.
Another question was
regarding interpreting the results in HFSS. When
you calculate the far-field characterisitics, HFSS
gives results in terms of Directivity, Gain and
'Realized Gain'. What does 'realized gain' mean?
I was confused, since, if you look at the efficiency
factor, it appears this is calculated using Directivity
and Gain and not realized gain.
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AP |
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Post subject:
Posted: Mon Jan 09, 2006 4:44 pm
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Sorry, I don't know about the realized gain...
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UWB_antenna_guy |
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Post subject:
Posted: Fri Jan 20, 2006 4:29 pm
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| Colonel |
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Joined: Tue Aug 09, 2005
1:07 pm
Posts: 28 |
Def. Realized Gain: When mismatch loss occurs,
as it usually does, this loss must be subtracted
from the power gain of the antenna to yield realized
gain. Realized gain is important to the systems
engineer, for it reveals how much signal will
be available at the input to the receiver for
a given field strength. See:
http://www.wj.com/pdf/technotes/Direct_antennas.pdf
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Karthik |
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Post subject:
Posted: Fri Jan 20, 2006 4:45 pm
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Posted 11/12/2012
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