Doctoral Dissertations

Date of Award

8-2008

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Electrical Engineering

Major Professor

Aly E. Fathy

Committee Members

Marshall O. Pace, Paul B. Crilly, Mohamed Mahfouz

Abstract

Flexibility of any proposed communication links is becoming one of the most challenging features. Direct broadcasting satellite services, for example, will be greatly enhanced by providing service-on-the-move. This market is very demanding as it necessitates the development of a low cost, low profile antenna that can be mounted on top of SUVs and minivans, which is capable of continuously tracking the satellite. Another example is the wireless antennas for laptops and smart-phones, where the antennas should fit within an extremely small volume and should be capable of addressing many services over wide frequency range. In this dissertation, both DBS and the wireless antennas are addressed.

In these studies, efforts have been concentrated in developing low profile planar antennas, in particular, slot arrays. Travelling wave slotted waveguide arrays have been utilized to minimize the scanning angle range limits due to their inherent beam tilt angle. CNC machines were utilized first to fabricate the early prototypes for sub-array developments. Subsequently, a low cost fabrication technology is adopted to develop a low cost and light weight full array using substrate integrated waveguides (SIWs). The SIW is fully characterized and an excellent equivalent model has been derived to allow easy "translation" of metallic waveguide components to SIW. Various SIW junctions, transitions, and arrays have been developed for array feed networks including a 64 radiating SIW full array and a 32 radiating SIW array with folded feed.

Meanwhile, for the wireless antennas, the utilization of reconfigurable hardware has been introduced to provide the required multi-functionality services and wide frequency coverage. Various reconfigurable antennas were developed and utilized to demonstrate their advantages compared to other design options such as wide-band or multi-band approaches. Both micro-electro-mechanical switches "MEMS" and "PIN" diodes have been successfully utilized to switch between the different configurations. The placement, control, and modeling of the switches are also discussed and novel modeling and biasing topologies are introduced.

A novel and practical concept of reconfigurable multiband antenna is introduced here too, where advantages of both the multi-band and the reconfigurable antenna structures can be simultaneously achieved while supporting more services.

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