AVALIAÇÃO DE PERFORMANCE DE ANTENA MICROSTRIP VESTÍVEL CONSIDERANDO CURVATURA CORPORAL

Abstract

This work evaluates the effects of the mechanical curvature imposed on a textile inset-fed microstrip patch antenna positioned over a human head phantom, simulating a typical situation in Wireless Body Area Network (WBAN) applications. Initially, the antenna geometrical parameters are defined under ideal free-space conditions, assuming a 5.8 GHz center frequency. Following, this work assesses the effects of body proximity and antenna curvature on operational characteristics, such as resonant frequency, bandwidth, and radiation pattern. The antenna design and evaluation employs finite-element method models. Most of the antenna geometrical parameters are analytically defined, but some are obtained using Nelder-Mead optimization. Furthermore, the resulting Specific Absorption Rate on the head is calculated and compared with international safety standards. Computational results show that the curvature of the antenna, when placed on the human head, causes a relevant shift on resonant frequency. Thereby, the initial antenna design must provide a sufficiently large bandwidth to account for such detrimental effect. Accordingly, the proposed antenna reached 790 MHz bandwidth (at the expenses of a thicker substrate), which ensures proper operation when applied over the body in WBAN applications. The designed antenna also yielded a 19 dB front-to-back ratio, minimizing brain radiation exposure