Title :
Radio wave propagation along mixed paths through a four-layered model of rain forest: an analytic approach
Author :
Li, Le-Wei ; Yeo, Tat-Soon ; Kooi, Pang-Shyan ; Leong, Mook-Seng
Author_Institution :
Dept. of Electr. Eng., Nat. Univ. of Singapore, Singapore
fDate :
7/1/1998 12:00:00 AM
Abstract :
This paper presents a novel full-wave analysis of the radio waves that are excited from a dipole antenna located in the trunk layer and propagate inside a four-layered forest medium. The dyadic Green´s functions for the four-layered 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 quasi-static approximation, saddle-point technique, and branch-cut 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 quasi-dynamic and complex images, are considered in the integration in the complex plane. Among those waves excited by a dipole antenna in the four-layered medium, it is shown theoretically and numerically that the lateral wave along the upper-side air-canopy interface plays a role of dominant modes. The propagation mechanism of other lateral waves due to the air-canopy, canopy-trunk, and trunk-ground 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
Keywords :
Green´s function methods; UHF radio propagation; VHF radio propagation; dipole antennas; tropospheric electromagnetic wave propagation; 100 MHz; 3 GHz; 500 MHz; air-canopy interface; branch-cut integrations; canopy-trunk interface; closed form; complex images; complex plane; dipole antenna; direct waves; dyadic Green´s functions; electric fields; four-layered forest medium.; four-layered model; full-wave analysis; integral expression; lateral waves; mixed paths; multiple reflected waves; quasi-dynamic images; quasi-static approximation; radio wave propagation; rain forest; saddle-point technique; trunk layer; trunk-ground interfaces; upper-side air-canopy interface; Antenna theory; Antennas and propagation; Dipole antennas; Frequency; Geometry; Nonhomogeneous media; Propagation losses; Rain; Solid modeling; Vegetation mapping;
Journal_Title :
Antennas and Propagation, IEEE Transactions on