Study Of Inhomogeneous Dielectric Resonators For Linearly Circularly Polarized Microwave Antenna Applications

In the last three decades a huge amount research has been dedicated to homogeneous (single permittivity) dielectric resonators (DRs) with cylindrical, rectangular/square and hemispherical shapes being the center of attention. These DRs have been investigated theoretically, numerically, and experimen...

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Main Author:	ULLAH, UBAID
Format:	Thesis
Language:	English
Published:	2016
Subjects:	T Technology
Online Access:	http://eprints.usm.my/46179/1/Study%20Of%20Inhomogeneous%20Dielectric%20Resonators%20For%20Linearly%20Circularly%20Polarized%20Microwave%20Antenna%20Applications.pdf
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spelling	my-usm-ep.461792021-11-17T03:42:18Z Study Of Inhomogeneous Dielectric Resonators For Linearly Circularly Polarized Microwave Antenna Applications 2016 ULLAH, UBAID T Technology In the last three decades a huge amount research has been dedicated to homogeneous (single permittivity) dielectric resonators (DRs) with cylindrical, rectangular/square and hemispherical shapes being the center of attention. These DRs have been investigated theoretically, numerically, and experimentally therefore, all the major performance controlling parameters are known for the homogeneous DRs. It well known that a homogenous DR can serve only one purpose at a time i.e. strong coupling to the source and hence narrow impedance bandwidth and vice versa. To overcome these drawbacks of homogenous DRs, in this work inhomogeneous DRs are designed in such a way that the basic geometry of the resonator is maintained so that the available theoretical, numerical and experimental analysis tools can be effectively applied to the proposed inhomogeneous DRs. The inhomogeneities in the resonators are introduced systematically in the azimuth (ϕ) direction so that the electromagnetic field distribution in the resonators remains the same with different range of energy confinement. To validate these ideas three different resonators based on cylindrical dielectric resonator (CDR) and rectangular/square shape resonators are investigated. For inhomogeneous CDR two 90ᴼ pie shape sectors of relatively high permittivity were introduced in the ϕ-direction in a way that sectors with same permittivity are placed in the opposite quadrant. Similarly, another inhomogeneous DR (split-oval shape) was designed by inserting high permittivity rectangular strip in the middle of two half cylindrical DR in the ϕ direction. Lastly, the third design of this research is based on a square shape DR in which the permittivity is lowered by introducing air-gap within the resonator which appears like a nested square DR. The proposed inhomogeneous DRs are tested for linearly polarized (LP) wideband antenna applications with a common excitation technique i.e. microstrip line. While, for circularly polarized (CP) designs, it is important to excite two orthogonal modes with the same amplitude hence different feeding techniques are used. Theoretical, numerical and experimental analysis of the inhomogeneous dielectric resonator antennas (DRA) showed that by properly designing inhomogeneous resonators, impedance bandwidth response, axial ratio (AR) bandwidth, gain and efficiency of the DRA‘s can be improved. For all three inhomogeneous LP DRA‘s approximately 56% impedance bandwidth was achieved which shows 80.5% enhancement of bandwidth over homogeneous DRAs with stable radiation characteristics throughout the operating band. The AR bandwidth response of the CP inhomogeneous DRA‘s was recorded to be 200% more than that of homogeneous counterparts. For the first two inhomogeneous DRAs gain was improved up to 6.5 dBi while for the nested square DR gain remained almost the same as that of the homogeneous square DR. With reference to these findings it was found that performance of the DRA can be noticeably improved with systematic introduction of inhomogeneity in the DR. 2016 Thesis http://eprints.usm.my/46179/ http://eprints.usm.my/46179/1/Study%20Of%20Inhomogeneous%20Dielectric%20Resonators%20For%20Linearly%20Circularly%20Polarized%20Microwave%20Antenna%20Applications.pdf application/pdf en public phd doctoral Universiti Sains Malaysia Pusat Pengajian Kejuruteraan Elektrik & Elektronik
institution	Universiti Sains Malaysia
collection	USM Institutional Repository
language	English
topic	T Technology
spellingShingle	T Technology ULLAH, UBAID Study Of Inhomogeneous Dielectric Resonators For Linearly Circularly Polarized Microwave Antenna Applications
description	In the last three decades a huge amount research has been dedicated to homogeneous (single permittivity) dielectric resonators (DRs) with cylindrical, rectangular/square and hemispherical shapes being the center of attention. These DRs have been investigated theoretically, numerically, and experimentally therefore, all the major performance controlling parameters are known for the homogeneous DRs. It well known that a homogenous DR can serve only one purpose at a time i.e. strong coupling to the source and hence narrow impedance bandwidth and vice versa. To overcome these drawbacks of homogenous DRs, in this work inhomogeneous DRs are designed in such a way that the basic geometry of the resonator is maintained so that the available theoretical, numerical and experimental analysis tools can be effectively applied to the proposed inhomogeneous DRs. The inhomogeneities in the resonators are introduced systematically in the azimuth (ϕ) direction so that the electromagnetic field distribution in the resonators remains the same with different range of energy confinement. To validate these ideas three different resonators based on cylindrical dielectric resonator (CDR) and rectangular/square shape resonators are investigated. For inhomogeneous CDR two 90ᴼ pie shape sectors of relatively high permittivity were introduced in the ϕ-direction in a way that sectors with same permittivity are placed in the opposite quadrant. Similarly, another inhomogeneous DR (split-oval shape) was designed by inserting high permittivity rectangular strip in the middle of two half cylindrical DR in the ϕ direction. Lastly, the third design of this research is based on a square shape DR in which the permittivity is lowered by introducing air-gap within the resonator which appears like a nested square DR. The proposed inhomogeneous DRs are tested for linearly polarized (LP) wideband antenna applications with a common excitation technique i.e. microstrip line. While, for circularly polarized (CP) designs, it is important to excite two orthogonal modes with the same amplitude hence different feeding techniques are used. Theoretical, numerical and experimental analysis of the inhomogeneous dielectric resonator antennas (DRA) showed that by properly designing inhomogeneous resonators, impedance bandwidth response, axial ratio (AR) bandwidth, gain and efficiency of the DRA‘s can be improved. For all three inhomogeneous LP DRA‘s approximately 56% impedance bandwidth was achieved which shows 80.5% enhancement of bandwidth over homogeneous DRAs with stable radiation characteristics throughout the operating band. The AR bandwidth response of the CP inhomogeneous DRA‘s was recorded to be 200% more than that of homogeneous counterparts. For the first two inhomogeneous DRAs gain was improved up to 6.5 dBi while for the nested square DR gain remained almost the same as that of the homogeneous square DR. With reference to these findings it was found that performance of the DRA can be noticeably improved with systematic introduction of inhomogeneity in the DR.
format	Thesis
qualification_name	Doctor of Philosophy (PhD.)
qualification_level	Doctorate
author	ULLAH, UBAID
author_facet	ULLAH, UBAID
author_sort	ULLAH, UBAID
title	Study Of Inhomogeneous Dielectric Resonators For Linearly Circularly Polarized Microwave Antenna Applications
title_short	Study Of Inhomogeneous Dielectric Resonators For Linearly Circularly Polarized Microwave Antenna Applications
title_full	Study Of Inhomogeneous Dielectric Resonators For Linearly Circularly Polarized Microwave Antenna Applications
title_fullStr	Study Of Inhomogeneous Dielectric Resonators For Linearly Circularly Polarized Microwave Antenna Applications
title_full_unstemmed	Study Of Inhomogeneous Dielectric Resonators For Linearly Circularly Polarized Microwave Antenna Applications
title_sort	study of inhomogeneous dielectric resonators for linearly circularly polarized microwave antenna applications
granting_institution	Universiti Sains Malaysia
granting_department	Pusat Pengajian Kejuruteraan Elektrik & Elektronik
publishDate	2016
url	http://eprints.usm.my/46179/1/Study%20Of%20Inhomogeneous%20Dielectric%20Resonators%20For%20Linearly%20Circularly%20Polarized%20Microwave%20Antenna%20Applications.pdf
_version_	1747821627231436800

Study Of Inhomogeneous Dielectric Resonators For Linearly Circularly Polarized Microwave Antenna Applications

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