Date of Award:

8-2012

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Electrical and Computer Engineering

Committee Chair(s)

Bedri A. Cetiner

Committee

Bedri A. Cetiner

Committee

Doran J. Baker

Committee

Jacob Gunther

Committee

Edmund Spencer

Committee

T.C. Shen

Abstract

Antennas are the most essential and significant elements of any wireless communication system. The most common antennas used in wireless communication systems include dipoles/monopoles, horn antennas, loop antennas, and micro-strip antennas. Each type possesses inherent advantages and disadvantages that make them satisfactory for particular applications. The properties of these antennas, however, are fixed by the initial design and cannot be changed. These fixed properties impose restrictions on the overall system performance as the antenna cannot adapt its characteristics in response to the changing propagation parameters of the wireless medium. A reconfigurable antenna, on the other hand, can dynamically change its properties in frequency, polarization, and radiation pattern, and therefore it can adapt its behavior to a winning set of parameters for a given propagation environment. For example, single antennas typically used in a cellular telephone are monopole or micro-strip-based antennas and may or may not have multi-frequency capabilities. The ability to tune the antenna’s operating frequency could be utilized to change operating bands, filter out interfering signals, or tune the antenna to operate in a new environment. If the antenna’s radiation pattern could be changed, it could be redirected toward the access point and use less power for transmission, resulting in a valuable saving in battery power. However, the development of these multi-functional antennas poses some challenges. These vi challenges lie not only in obtaining the desired levels of antenna functionality but also in the implementation of the antenna.

This dissertation work builds upon the theoretical and experimental studies of radio frequency micro- and nano-electromechanical systems (RF M/NEMS) integrated multifunctional reconfigurable antennas (MRAs). This work focuses on three MRAs with an emphasis on a wireless local area network (WLAN), 5-6 GHz, beam tilt, and polarization reconfigurable parasitic layer-based MRA with inset micro-strip feed. The other two antennas are an X band (8-12 GHz) beam steering MRA with aperture-coupled micro-strip fed and wireless personal area network (WPAN), 60 GHz, inset micro-strip fed MRA for dual frequency and dual polarization operations. For the WLAN (5-6 GHz) MRA, a detailed description of the design methodology, which is based on the joint utilization of electromagnetic (EM) full-wave analysis and multi-objective genetic algorithm, and fundamental theoretical background of parasitic layer-based antennas are given. Various prototypes of this MRA have been fabricated and measured. The measured and simulated results for both impedance and radiation characteristics are given. The work on the MRAs operating in the X band and 60 GHz region focuses on the theoretical aspects of the designs. Different than the WLAN MRA, which uses inset fed structure, the aperture-coupled feed mechanism has been investigated with the goal of improving the bandwidth and beam-tilt capabilities of these MRAs. The simulated results are provided and the working mechanisms are described. The results show that the aperture-coupled feed mechanism is advantageous both in terms of enhanced bandwidth and beam-steering capabilities. Finally, this dissertation work concludes with plans for future work, which will build upon the findings and the results presented herein.

Checksum

22416d03af0b04f97857d2cbb896231d

Comments

This work made publicly available electronically on September 20, 2012.

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