High-frequency asymptotic solution for scattered fields by a discontinuity of a planar impedance surface

Abstract

Medium-frequency (MF) and high-frequency (HF) ground wave propagation is playing and will continue to play one of the most important roles for a long distance communication. When the ground wave traverses a coastline, the ground wave is strongly affected by the abrupt change of the surface impedance of the earth's surface [1] – [4]. The mixed-path theory [3] has been used widely to obtain the ground wave propagation over the land to sea mixed-path. Both the source and observation points are placed on or near the earth's surface [2], [3], [5], [6]. In this paper, by applying the aperture field method and the saddle point technique [7], we shall derive a novel asymptotic solution with higher-order terms for the high-frequency scattered fields by an impedance discontinuity of a planar surface [8] – [10]. We will assume that both the transmitting and receiving antennas are placed at arbitrary heights from the earth's surface [8] – [10]. In order to obtain the accurate solution, we will newly derive the higher order terms. The validity and the utility of the novel asymptotic solution are confirmed by comparing with the reference solution calculated from the numerical integration.