Radio wave propagation along mixed paths through a fourlayered model of rain forest: An analytic approach

Abstract

This paper presents a novel fullwave analysis of the radio waves that are excited from a dipole antenna located in the trunk layer and propagate inside a fourlayered forest medium. The dyadic Green's functions for the fourlayered geometry are applied first to derive the integral expression of the electric fields. The closed form of the electric fields is then obtained by using the quasistatic approximation, saddlepoint technique, and branchcut integrations in the complex plane and, hence, expressed in terms of direct waves, multiple reflected waves, and lateral waves. Two kinds of images, i.e., the quasidynamic and complex images, are considered in the integration in the complex plane. Among those waves excited by a dipole antenna in the fourlayered medium, it is shown theoretically and numerically that the lateral wave along the upperside aircanopy interface plays a role of dominant modes. Propagation mechanism of other lateral waves due to the aircanopy, canopytrunk, and trunkground interfaces is also discussed and analyzed so as to gain an insight into the wave characteristics. Transmission losses of the lateral waves are calculated numerically. © 1998 IEEE.