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Enhancement TE
10
Transmission of X-Band Guided Waves
Structure Using Mode Extractor-Converter
Hassan M. Elkamchouchi
1
Yasser M. Madany
2
Ahmed F. Miligy
3
1
Senior, Member IEEE, Communications and Electronics Depart., Alexandria university, Egypt, e-mail: helkamchouchi@ieee.org.
2
Member IEEE, Communications and Electronics Department, Alexandria university, Alexandria, Egypt, e-mail: ymadany@ieee.org.
3
Communications and Electronics Department, Alexandria university, Alexandria, Egypt, e-mail: ahmed_miligy73@yahoo.com.
Abstract The waveguide antenna arrays provide a number of
advantages in many radar, remote sensing and satellite
applications. The advantages are related with the antenna
planar form, strength of the construction, high power
operation capability, high efficiency, small thickness and
weight. In this paper, guided waves with enhancement TE
10
transmission using mode extractor-converter structure has
been introduced and analyzed using the full 3D
electromagnetic field inside a structure based on the finite
element method. The proposed structure presents TE
10
enhancement transmission coefficient ratio up to 18.74, 22.44
and 26.56 for cylindrical, cone and horn transition waveguide
channel compared to the conventional waveguide feeder. The
proposed structure characteristics such as transmission
coefficient, the magnitude of electric field are obtained to
demonstrate the performance without and with different mode
extractor-converter designs.
1 INTRODUCTION
Modern communication and radar antennas employ
highly sophisticated feed systems. The feed design
quality continues to be critical to the antenna overall
performance. At higher microwave frequencies,
waveguide is a transmission medium, mainly due to
its low RF loss and high power handling capability.
Over the recent decade a significant research effort
was invested for waveguide components and entire
feed systems [1]-[4].
In this paper, guided waves with enhancement TE
10
transmission using mode extractor-converter
structure has been introduced and analyzed using
HFSS simulator [5]. The proposed feeder structure
has been designed to meet the requirements for X-
band array waveguide radar antenna applications [6]-
[7] at operating frequency band 11-12 GHz. There
are several constraints on the design including mode
purity; these are not convenient for the design
process. It is possible to propagate several modes
TE
10
, TE
01
and TE
20
of electromagnetic waves within
a structure. The physical dimensions of a structure
determine the cutoff frequency for each mode. If the
frequency of the impressed signal is above the cutoff
frequency for a given mode, the electromagnetic
energy can be transmitted through the guide for that
particular mode with minimal attenuation.
Otherwise, the electro-magnetic energy with a
frequency below cutoff for that particular mode will
be attenuated to a negligible value in a relatively
short distance. The dominant mode TE
10
in a
particular structure is the mode having the lowest
cutoff frequency. The power of TE
10
, TE
01
and TE
20
modes is combined into the proposed structure. To
enhance the dominant mode TE10 transmission,
higher modes of the combined power is extracted
from the line using mode extractor at specific
position and converted into TE
10
mode which was
injected to the same line at another position. The
proposed guided waves structure characteristics such
as transmission coefficient, the magnitude of electric
field are obtained to demonstrate the performance
without and with different mode extractor-converter
designs.
2 GUIDED WAVES DESIGN STRUCTURE
In order to achieve the widest possible usable
bandwidth for the TE
10
mode, the bandwidth interval
is [f
10
, 2f
10
]. Commonly used rectangular waveguides
have an aspect ratio (height /width) of approximately
0.5 and λ
g
= 111.52 mm.
2.1 Without mode extractor-converter
Figure 1: The main dimensions of the proposed
structure without mode extractor-converter.
The unit cell guided waves structure is basically
composed of an input and two horizontal linear
coupled output ports denoted by 1, 2 and 3, respect-
ively. The ports dimension is 28.125 14.0625 mm
978-1-61284-978-2/11/$26.00 ©2011 IEEE
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