Multi-functional slot spiral -based antennas for airborne and automotive applications.

In this thesis, several two-arm slot spiral-based antennas for broadband, multi-band and narrow-band operations are developed. Such antennas are aimed at satisfying new requirements for airborne and automotive applications. Specifically, an Archimedean slot spiral is analyzed and developed using computational and experimental studies to improve its low and high frequency operation. A meanderline concept is introduced and combined with other techniques to obtain antenna bandwidth in excess of 100:1 for a multi-functional VHF to S-band aircraft based radar/communication system. New feeding techniques are also developed for the excitation of the 2 nd spiral mode for use in automotive based applications. More specifically, a two arm slot spiral is designed and optimized for multi-band/broadband performance in terms of the input impedance and pattern requirements. It is demonstrated that the inherently broadband radiating structure of the slot spiral can be modified for simultaneous dual-band operation for two resonant, narrow-band systems. It is also demonstrated that this feeding can be easily redesigned for pattern steering at a single frequency, or for the frequency steering operation. Finally, instead of using a single multi-functional spiral and a single cavity, an alternative is to employ multiple cavities to accommodate the different bands and thus allow for more degrees of freedom in the design process. In the context of this modified concept, the bands requiring circularly polarized performance are radiated by a spiral section of the aperture, whereas those restricted to vertical polarization are configured to radiate from a different section and cavity. The radiation elements in the different cavities are then designed to achieve the required pattern and gain performance without adversely affecting coupling among the bands. In comparison to commercially available antennas, the antenna is unique in being small, conformal and integrated. This so called combo-antenna is aimed for simultaneous reception of the SDARS (S&barbelow;atellite D&barbelow;igital A&barbelow;udio R&barbelow;adio S&barbelow;ervices) system and DAB (D&barbelow;igital A&barbelow;udio B&barbelow;roadcasting) system, for automobile based receivers.PhDApplied SciencesElectrical engineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/131810/2/3057944.pd