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Design Methodology for Wideband Electrically Small Antennas (ESA) Based on the Theory of Characteristic Modes (CM)

Obeidat, Khaled Ahmad
http://rave.ohiolink.edu/etdc/view?acc_num=osu1274730653

Abstract Details

2010, Doctor of Philosophy, Ohio State University, Electrical and Computer Engineering.
Emerging broadband applications with market pressures for miniaturized communication devices have encouraged the use of electrically small antennas (ESA) and highly integrated RF circuitry for high volume low cost mobile devices. This research work focuses on developing a novel scheme to design wideband electrical small antennas that incorporates active and passive loading as well as passive matching networks. Several antennas designed using the proposed design technique and built and measured to assess their performance and to validate the design methodology. Previously, the theory of Characteristic Modes (CM) has been used mostly for antennas analysis. However; in this chapter a design procedure is proposed for designing wide band (both the input impedance bandwidth and the far field pattern bandwidth) electrically small to mid size antennas using the CM in conjunction with the theory of matching networks developed by Carlin. In order to increase the antenna gain, the antenna input impedance mismatch loss needs to be minimized by carefully exciting the antenna either at one port or at multiple ports and/or load the antenna at different ports along the antenna body such that the Q factor in the desired frequency range is suitable for wideband matching network design. The excitation (feeding structure), the loading of the antenna and/or even small modifications to the antenna structure can be modeled and understood by studying the eigenvalues and their corresponding eigencurrents obtained from the CM of the antenna structure. A brief discussion of the theory of Characteristic Modes (CM) will be presented and reviewed before the proposed design scheme is introduced. The design method will be used to demonstrate CM applications to widen the frequency bandwidth of the input impedance of an electrically small Vee shape Antenna and to obtain vertically polarized Omni-directional patterns for such antenna over a wide bandwidth. A loading technique based on the CM to either design frequency reconfigurable antennas or broaden their bandwidth by Non-Foster loading will also be discussed as part of the design methodology. In the Appendix, a brief discussion of the fundamental limits of electrical small antennas is presented and then followed by a discussion of the fundamental limits of the impedance bandwidth of the ESA when a passive matching network is used. Matching network implemented using Non-Foster matching is also discussed in the appendix.
Roberto G. Rojas, PhD (Advisor)
Garbacz Robert, PhD (Committee Member)
Teixeira Fernando, PhD (Committee Member)
118 p.
Electrical Engineering; Engineering; Experiments
Theory of Characteristic Modes; electrically small antennas; Matching Network; Parallel Resonance; reconfigurable antenna; wideband antenna; conformal antenna; non-foster loads; NIC; Cavity modes; Patch antenna; loop antenna; PIFA

Recommended Citations

Citations

  • Obeidat, K. A. (2010). Design Methodology for Wideband Electrically Small Antennas (ESA) Based on the Theory of Characteristic Modes (CM) [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1274730653

    APA Style (7th edition)

  • Obeidat, Khaled. Design Methodology for Wideband Electrically Small Antennas (ESA) Based on the Theory of Characteristic Modes (CM). 2010. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1274730653.

    MLA Style (8th edition)

  • Obeidat, Khaled. "Design Methodology for Wideband Electrically Small Antennas (ESA) Based on the Theory of Characteristic Modes (CM)." Doctoral dissertation, Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1274730653

    Chicago Manual of Style (17th edition)

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© 2010, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.