Scattering of a Pulsed Beam By a Random Medium Over Ground

• Published in: Journal of electromagnetic waves and applications Vol. 15; no. 4; pp. 481 - 516
• Main Authors: Kilic, O., Lang, R.H.
• Format: Journal Article
• Language: English
• Published: Zeist Taylor & Francis Group 01.01.2001; VSP
• Subjects: Applied classical electromagnetism; Applied sciences; Diffraction, scattering, reflection; Electromagnetic wave propagation, radiowave propagation; Electromagnetism; electron and ion optics; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Physics; Radiocommunications; Radiowave propagation; Telecommunications; Telecommunications and information theory; Gaussian beam; Pulse response; Wave scattering; Electromagnetic pulses; Plane waves; Aperture antennas; Random medium
• ISSN: 0920-5071; 1569-3937
• DOI: 10.1163/156939301X00779

Transient response of a random medium to a narrowband short pulse is examined for an aperture antenna overlooking a discrete random medium with a flat surface beneath. The study is an attempt to model pulsed radar applications looking at the earth by representing the antenna realistically. The actual antenna pattern is taken into account by modeling the radiation pattern as a Gaussian beam. The backscatter case is considered and the same antenna is used for both transmit and receive purposes. The scattered fields from the medium are calculated by using the analytical wave theory in conjunction with the distorted Born approximation. The spread of the beam within the medium and the variation of its intensity with propagation direction is accounted for by decomposing the beam into plane waves travelling in different directions and by making use of the well studied plane wave solutions to the problem. Compared to models that use the radiative transfer approach, the model takes the enhancement effects into account. As opposed to the pencil beam representation of the incident field, the model is a more realistic representation of the illuminating fields and can handle the special case of nadir looking antennas, where the former method fails. Individual scattering contributions from volume and ground are identified. Coherent and incoherent responses from the medium are determined by identifying the components of the received power that depend on the mean and fluctuating components of the illuminating field. Numerical results are presented and the behavior of different scattering mechanisms is examined for various medium conditions.