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[pic] can you determine what kind of this antenna

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bepsml

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dear all

i formed the antenna with no ground plane on bottom side, and I got good S11 after add a patch beside a feedline
can you determine what kind of this antenna, what a patch beside the feed can be called?

http://oi46.tinypic.com/2cyifpg.jpg

thank you
 

zorro

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Hi bepsml,

I would say that it could be called a sort of modified fat monopole.
Is the length something less than a quarter wavelength?
Is the polarization predominantly vertical?

I think that the patch would act as an element that helps to match impedance.
I have curious to know how you came to this configuration.

Remember that not only s11 is of interest. Also radiation pattern, bandwidth and polarization.
Regards

Z
 

bepsml

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thank very much for reply Z

yes the feed length is less than a wavelength
i try to design an uwb antenna by a rectangular planar, after doing some modification, and finally got about 60% of fractional BW without forming a groundplane even adding that patch, migh this design classified as a valid antenna :D?

by the way can i ask a ref which mention how a formulation to forming a ground plane, cz i stuck to get good BW with a ground on back side for my substrate with a fixed dimension
 

zorro

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yes the feed length is less than a wavelength
How much (in wavelengths of the central frequency) is the side of the big square?

i try to design an uwb antenna by a rectangular planar, after doing some modification, and finally got about 60% of fractional BW without forming a groundplane even adding that patch,
ok, but I'm intriged by the shape. How was it motivated?

...migh this design classified as a valid antenna :D?
Let me quote something appeared from an old book, and quoted in the preface of the book Phased Array Antenna Handbook (First Edition) by Mailloux:

Any pile of tin with a transmission line exciting it may be called an antenna. It is
evident on physical grounds that such a pile of tin does not make a good antenna,
and it is worthwhile to search for some distinguishing characteristics that can be
used to differentiate between an ordinary pile of tin and one that makes a good
antenna.


Regards

Z
 
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bepsml

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excuse me "the side of the big square"?
ya from fc it solved, l feed, l shape = 0.18, 0.16 lambda, l patch (big square?) = 0.54 lamda
l shape = w feed

it just when i reviewing about CPW with no ground, then I adding that shape, and it worked :D

so according to achieved parameter like radiation pattern, BW etc, is the antenna can be said has a good antenna characteristic?
although I realize that is unusual design maybe
 
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zorro

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patch (big square?) = 0.54 lamda
So it seems that it acts like a patch rather than a monopole, at least at central frequency.
Maybe the dominant mode changes with frequecy, and so the radiation characteristics (pattern, polarization).

so according to achieved parameter like radiation pattern, BW etc, is the antenna can be said has a good antenna characteristic?
although I realize that is unusual design maybe
Yes. Yet, usually the conceptual design has a rationale, and adjustmens are made by optimization or trial-and-error.
Regards

Z
 

bepsml

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OK great thank for your answer Z

maybe this tons of theory but can you give me a simple explanation how to determine that a shape act as monopole or patch please

once again I say thank before and after :D
 

zorro

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As a rule of thumb:
The length of a monopole is about (a bit less than) 1/4 wavelength from ground plane to top.
The resonant side of a patch is about (a bit less than) 1/2 wavelength.
Regards

Z
 
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