Abstract

This thesis provides several designs of broadband microstrip antennas for the use in WLAN applications. It also highlights the novel reconfigurable microstrip antenna design. The main objective of this thesis is to design a novel microstrip antenna that is broadband, circularly polarized, multiband, reconfigurable and easy-to-fabricate. The thesis, in the first stage, presents a review of various different options available when designing and manufacturing wideband microstrip antennas. The review includes basic theory of microstrip patch antennas, matching techniques and broadbanding techniques. The second stage concentrates on the development of a couple of working prototype antenna designs and finally presents the design of a reconfigurable antenna that can perform over several frequency bands. The shapes of broadband patch antennas used are rectangular, circular and triangular. The multiple resonance technique is used in the design of the broadband antennas. Numerical and measured results are presented and discussed. The proposed patch antennas give measured bandwidth up to 28.5%. The reconfigurable antenna on the other hand is designed to possess frequency and polarization reconfigurability, and can operate in six different frequency bands. In addition to the bandwidth advantage, the proposed configuration offers easy reconfigurability with the ability to exclude switches in the combination part of the feed network. The important aspect of this design is that it provides a high size reduction for all the operating frequencies compared to conventional rectangular patches. Besides compactness all proposed antennas have gain better than 7dB. The proposed antennas are found to be suitable for WLAN standards.