# A reciprocity approach for analyzing radiation from aperture and nicrostrip antennas.

Abstract (Summary)

Conformal antennas, used extensively on mobile communications systems, generally
have complex configurations and are often times mounted on or used within large
structures. Hence, the modeling of such antennas is a challenging problem. The most frequently
used numerical techniques either require excessive computational resources or
cannot effectively model such structures. Thus, hybrid techniques have recently been
employed to take advantage of each method’s strengths, while minimizing weaknesses.
To enhance computational efficiency, a new methodology is introduced in this
thesis, based on a combination of the Finite Difference Time Domain (FDTD) and the
Method of Moments (MoM) numerical techniques in conjunction with the Surface
Equivalence and Reciprocity Theorems. Several antenna configurations are considered to
illustrate the new methodology: 1) radiating slots on conducting cylinders, 2) microstrip
patch antennas mounted on large conducting structures, and 3) reflector antennas with
partial circular symmetry.
In the transmit mode, the region containing the radiation source is first analyzed
using either the MoM or FDTD technique to determine “equivalent currents” at the radiating
aperture. The Surface Equivalence Principle is then applied, allowing the material
in the radiating region to be theoretically modified to match its surroundings. This creates
a homogeneous structure for the first two antenna types, and a circularly symmetric structure
for the last type.
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The operation of the antenna system is then reversed to the receive mode, and the
fields produced at the radiating aperture are determined. By analyzing this mode of operation,
difficult integrals and asymmetric sources are avoided for antenna types 1 and 2,
and 3, respectively. For antenna types 1 and 2, the MoM technique is used to compute the
surface fields, which reduces computational resource requirements since the surface of
the structure – as opposed to its volume – is modeled. For antenna type 3, the effective
removal of asymmetric sources allows a 2-D FDTD simulation of the antenna structure,
instead of a full 3-D model.
Finally, utilizing the Reciprocity Theorem, the surface fields determined for the
receive mode case are combined with the “equivalent currents” calculated in the transmit
mode in order to compute far-zone fields. Through use of the technique, computational
savings on the order of 95% are realized.
Bibliographical Information:

Advisor:

School:Pennsylvania State University

School Location:USA - Pennsylvania

Source Type:Master's Thesis

Keywords:

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