Design of a Directional Antenna Based on a Resonance Based Reflector and Its Applications on Bio-Electromagnetics

Abstract

A wideband resonance-based reflector (RBR) is proposed in this paper. It has an inphase reflection band from 2.61 GHz to 5.59 GHz (72.68%), while high reflection magnitude is also obtained in the band. The proposed RBR was applied to an elliptical monopole antenna, and then, the omnidirectional radiation patterns are transformed to be unidirectional ones. The antenna profile is only 0.12λ. The proposed antenna has a measured impedance band of 2.12 GHz to 6 GHz (95.57%) and a measured front-to-back ratio band (FBR > 10 dB) of 2.2 GHz to 4.68 GHz (72.09%). The maximum FBR is up to 27.21 dB, and the antenna has good radiation performances. In addition, the proposed antenna is applied to investigate the electromagnetic characteristics of a human head. The transmission characteristics of electromagnetic wave in human head and the interactions between the human head and the electromagnetic wave were studied. The field distribution and specific absorption rate (SAR) are also discussed. Research found that the antenna matched well with the human head as good field distribution and propagation characteristics were obtained, and the antenna meets the safety standards.