Closely Coupled Multi-Mode Radiators: A New Concept for Improving the Performance of Electrically Small Antennas.

摘要

This document is the first interim research performance report of the Young Investigator Program (YIP) project funded by the Office of Naval Research. In this reporting period, we focused on examining the performance of the dual-mode conformal, ultra-broadband miniaturized antenna (CUBMA) in its common and differential modes of operation. The impact of the frequency- dependent mode combining feed network on the performance of the antenna was also examined. It was demonstrated that an optimum feed network exists, which can considerably enhance the response of the antenna in its differential mode and offer broadband impedance matching in the differential mode. The effect of using a PEC, PMC, and a composite PEC/PMC ground plane on shaping the radiation characteristics of the antenna in its differential mode of operation were theoretically examined. We demonstrated that in each cases, the radiation characteristics of the antenna in the differential mode can be tailored to enhance the vertically polarized radiation from the antenna along the azimuth plane. This is instrumental in making the radiation characteristics of the antenna in the differential mode similar to that of the common mode. Additionally, the effect of antenna-platform coupling was also investigated and antenna/platform decoupling techniques were developed for the cases where this coupling constituted a significant problem. Finally, two prototypes of a dual- mode CUBMA, which utilizes a PEC ground plane and an appropriate frequency- dependent mode combining network, were fabricated and tested. It was demonstrated that the proposed frequency-dependent mode-combining feed network can successfully be used to feed the dual-mode CUBMA in the appropriate mode of operation based on the frequency of the excitation signal.