Antenna Array Designs For Directional Wireless Communicatoin

Abstract

Forty percent of people living in rural areas do not have broadband Internet access. Availability of affordable broadband access to the Internet would have a significant impact on enabling the economic development in these areas and in providing improved quality of life. However, large-scale deployment of broadband wireless technologies hinges on the development of reliable, low cost, and energy efficient networking solutions. To overcome wireless networking challenges in rural areas, a novel advanced directional networking technology has been proposed. The approach is based on enhancing intelligence and logic capabilities in the physical layer in the OSI Model and without causing changes in the other layers of the communication networking model. A critical component in implementing the proposed system is the development of a low-cost and low-profile circularly polarized antenna array with beam-switching/beam-steering capabilities. In this dissertation, a broadband long-slot antenna array fed by simplified microstrip structures was designed, fabricated and a prototype was tested in the HCAC indoor antenna range. For system components requiring extremely low-profile antenna installations, a narrower-band high-gain stacked patch antenna array with annular gap was also developed. Both antenna arrays were tested for beam-steering capabilities using a new design of a broadband microstrip-based 8×8 Butler matrix with compact crossovers. The antenna arrays and the Butler matrix were fabricated and experimentally characterized. Simulation results were verified with measured data. The long-slot antenna array has 40% bandwidth with an average gain of 17 dBic and an axial ratio of < 1.8 dB. The stacked patch antenna array has 16.7% bandwidth with an average gain of 23 dBic and an axial ratio of < 1.6 dB. Stable radiation patterns and a scanning range of ±30° were obtained when the antenna arrays were fed by the Butler matrix.