[1] The space formed by the ground and ionosphere is known to act as a resonator for extremely low frequency (ELF) waves. Lightning discharges trigger this global resonance, which is known as Schumann resonance. Even though the inhomogeneity (like day-night asymmetry, local perturbation, etc.) is important for such a subionospheric ELF propagation, the previous analyses have been always made by some approximations because the problem is too complicated to be analyzed by any exact full-wave analysis. This paper presents the first application of the conventional numerical FDTD method to such a subionospheric ELF wave propagation, in which any kind of inhomogeneity can be included in this analysis. However, the present paper is intended to demonstrate the workability of this method only for a uniform waveguide (without day-night asymmetry), by comparing the results from this method with those by the corresponding analytical method.
This paper is concerned with an analysis of scattered waves from an aircraft by using the Ray-Tracing Method (RTM) based on the imaging method. In order to reduce computation time, we propose a simple algorithm for rapid ray searching. In this paper, we describe a concept of a proposed method and show a numerical simulation of scattered powers in a large analytical region. Moreover, as one example, we show a measurement result of scattered powers which was performed in the Tokyo Bay area. Comparing the numerical result with the experimental one, we investigate the accuracy of the proposed method.
The space formed by the ground and ionosphere is known to act as a resonator for extremely low frequency (ELF) waves. Lightning discharges trigger this global resonance, which is known as Schumann resonance. Even though the inhomogeneity (like day-night asymmetry, local perturbation etc.) is important for such a subionospheric ELF propagation, the previous analyses have been always made by some approximations because the problem is too complicated to be analyzed by any exact full-wave analysis. This paper presents the application of the conventional numerical FDTD (finite difference time domain) method to such a subionospheric ELF wave propagation, in which any kinds of inhomogeneities can be included in this analysis. The present paper is intended to demonstrate the workability of this method for a realistic waveguide (with daynight asymmetry), by comparing the results from this method with those by the corresponding analytical method.
This paper describes an activity of passive surveillance system in Japan. Electric Navigation Research Institute (ENRI) started the feasibility study of the passive surveillance system to be a conventional primary surveillance radar (PSR) alternative. The representative system among its technologies is a multi-static primary surveillance radar (MSPSR) which achieves higher update rates and higher detection rates including low level flights than those of the current PSR. The MSPSR is classified into passive bi-static radar (PBR), and it is operated by combining some transmitters or some receivers. Radio waves of the conventional PSR are suitable resources of operating frequency. Therefore, ENRI has investigated passive PSR. In this paper, we introduce our recent works and show some results of experiments carried out in the Sendai and Nagoya areas in Japan. In the experiments, we investigated the advantages of the passive PSR. First, we introduce experimental environment and experimental setup. Next, we show experimental results. Results show high performance of the passive PSR system where the passive secondary surveillance radar (SSR) was unable to carry out positioning. Finally, we discuss the passive PSR potential.
This paper is concerned with an algorithm for analyzing reflected and diffracted fields from a polyhedron type of target above a plane-ground. First, the numerical method for computing electromagnetic field is introduced. In the electric field computation, we use the conventional Fresnel reflection coefficient for reflection and the Fresnel function for diffraction which can precisely solve the diffracted field. Then an algorithm for searching rays between a transmitter and a receiver via a target is proposed. In that method, all the diffracted rays in LOS region from both transmitter and receiver are included when the electric field intensities are calculated. And reflected fields are also included in that solution in case they exist at the surface of a target. Finally, some numerical examples are shown.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.