| Conformal multifunctional antennas are greatly desired for man-portable, vehicular, and wireless sensor applications since they can support the functions of multiple antennas with the use of a single aperture. This eliminates inter-antenna mutual coupling while reducing size, cost, and complexity. The most significant challenges in multifunctional antenna research are to achieve the required bandwidth, radiation pattern, gain, and polarization at each operating frequency band with a single antenna aperture. Antennas must also be designed considering their mounting platforms, which greatly alter performance characteristics.;In this dissertation the concept of achieving multifunctional operation by antenna geometrical optimization is studied first by developing full-wave three dimensional electromagnetic models of the antenna and its integrating platform, such as vehicles and wireless sensor circuit boards. Several antennas and associated circuits are designed, fabricated, and tested to demonstrate multifunctional performance for applications ranging from land mobile radio to wireless sensors. The solutions proposed in this category include linearly polarized antennas with omnidirectional and directional pattern coverage at 225 and 450 MHz for vehicular application and miniature wideband circularly polarized microstrip patch antennas for wireless sensor application.;In the second part of this dissertation a novel switched multifunctional antenna is introduced where a wideband stacked microstrip patch is reconfigured for operation in two frequency bands to support wireless power beaming and data communication to sensors. First, the principles of reconfiguration is illustrated by constructing full-wave simulation models followed by experimental measurements on working prototypes switched with the help of high frequency PIN diodes. It is demonstrated that the reconfigurable antenna has excellent bandwidth, pattern, and gain characteristics to support a directional high gain operation at 5.7 GHz and another nearly omnidirectional, moderate gain operation at 2.45 GHz. This design is scalable in frequency and hence directly relevant to other applications, such as satellite handheld terminals and land mobile radio. Finally, the concept of using our switched multifunctional antenna to beam wireless power to sensors is demonstrated by designing, developing, and testing a high-frequency rectifying circuit integrated with the antenna. Measured results indicate that power transmission conversion efficiency in excess of seventy percent can be readily achieved at 5.7 GHz along with more than adequate high-speed data communication bandwidth at 2.45 GHz. |
