HFSS Dielectric Antenna PeakGain problem

[felvanin]

bended structure hfss

Dear all,

it is the first time i use this site and i hope to find some help.

i have simulated a dielectric antenna with HFSS.
Everything looks fine:
input impedance looks great (real part 50 ohm, imaginary part is zero at resonance).
S-parameters also look great 20dB return loss

the antenna is feed with a 50ohm coaxial cable.

i put the radiation boudary quite large and far from teh antenna (lambda/4 distance) and the gain looks ok.

the problem i have is the peack gain, if i plot it over frequency, i get a MINUMUM at resonance. this cannot be, and i should have a maximum of gain where i have a minimum of return loss.

anobody can help?

thanks

felvanin

 

[jallem]

hfss peakgain

That happens to me too....a while ago....
I could not find any explanation, some of my
especulations are that the antenna is not
efficient in radiation. It accepts the whole energy but
it does not put in a far field way.
I found some while ago someone that was experimenting
with antennas no effectives. In othe words, it was some
sore of antenna that radiates mostly near field and the
far fields were minimum, so creating a "cloud", or a close
area where the antenna communicates. This application
would be appropiate for example when a person has a
headphone in his head(of course) and a DVD player in
his belt. This might explain it.
I did some simulations of a very simple antenna as a dipole
and the same dipole bended as is normally used in some
miniaturization techniques. Well, the bended antenna was
as good as the straigh one in absorbing energy but was not
as good as radiating it. The efficiency went down. Maybe we
can share the files.

 

[felvanin]

bended antenna

i am glad that somebody had the problem.

the antenna gets the enrgy but it does not put it in the far field! that is what happen to me. i think that there is a problem in feeding the structure, or inaccuracy of the simulation.

i have calculated that my antenna should have 1 ohm of radiative resistance, and that should provide me 4 dB in the far field!

i still believe there is problem of software.

regarding your dipole, it is clear that if you bend it yo have the "image" of the current in opposide direction. this means that you lose radiation in the far field. check ur radiative resistance so that you know what you should expect from the simulation.

F

 

[yashar_zh]

Hi
I have such a problem too .
I simulated a monopole antenna with a band notch in hfss 10.
The return loss plot is ok but at the frequency that I want to filter it (notch) peak gain did not show any change.
Did you find any solution to this problem?

Added after 9 minutes:

Hi
I have such a problem too .
I simulated a monopole antenna with a band notch in hfss 10.
The return loss plot is ok but at the frequency that I want to filter it (notch) peak gain did not show any change.
Did you find any solution to this problem?
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