Date of Award

Spring 1999

Document Type

Thesis

Degree Name

Master of Science in Electrical Engineering - (M.S.)

Department

Electrical and Computer Engineering

First Advisor

Edip Niver

Second Advisor

Sirin Tekinay

Third Advisor

Raashid Ahmed Malik

Fourth Advisor

Necdet Uzun

Fifth Advisor

Alatan Lale

Abstract

Dual frequency bi-orthogonally polarized antenna to be used in Global Positioning System applications operating in Li (1575.42 ± 10.23 MHz) and L2 (1227.60 ± 10.23 MHz) Bands has been studied. To ensure compatibility with existing applications, the antenna size is limited in dimensions to 4.120" x 4.680" x 1.250" including the radome. Orthogonally placed two dual frequency probe excited patches were designed using a high dielectric constant substrate (ε r = 9.8 and thickness of 250 mils, Rogers TMM10i material) to obtain vertical and horizontal polarization for each band. The measured performance of this antenna showed good agreement with the specifications required to meet the application needs. As an attractive alternative a stacked dual patch antenna configuration has been suggested and a prototype antenna has also been developed. Using low and high dielectric constants of 2.20 and 9.8 and relative thicknesses of 125 and 250 mils for each layer an orthogonally placed dual patch configuration has been designed, fabricated and tested on a 2 square feet ground plane. Effects of radomes using materials with different permittivities have been studied through numerical simulations and radomes have been fabricated using plastic materials including UMHW, HDPE and Delrin. Numerical simulations have been carried out using IIE3D software package developed by Zeland Software Inc. Antennas that were fabricated based on optimized parameters have further required tuning due to inaccuracies in simulation and material properties. The measurement setup has been enhanced to accommodate axial ratio measurements in polarization pattern characterization by adding a rotary joint to rotate a linearly polarized antenna operating in the receiving mode. The performance characteristics showed that adequate bandwidths and beam widths were obtained and gain of these antennas were measured to be in the order of 3.5 dBi along the main lobe. Further work is continuing to obtain antennas with wider bandwidths using thicker substrates.

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