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Simulation Study on Ground-Based Direction Finding of VLF/ELF Radio Waves by Wave Distribution Functions: a Bayesian Approach
Mehrez HIRARI Masashi HAYAKAWA
IEICE TRANSACTIONS on Communications
Publication Date: 1995/06/25
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Antennas and Propagation
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In this paper we consider the determination of direction of arrival of VLF/ELF radio waves and their energy distribution at the ionospheric base by means of the inversion of electromagnetic data observed on the ground. The observed data are too limited, leading us to deal with a severely ill-posed problem similar to those encountered in digital image enhancement and computerized tomography. To handle this situation, the a priori information if available, is supposed to bring as much weight as the observed data do. We used a regularization based on Bayesian information criterion to reconstruct the wave distribution function at the ionosphere, that is, to determine the wave arrival direction. Using computer-generated data, two main results were obtained: first, the electromagnetic field data observed on the ground are sufficient to give a good approximation to the exit region of VLF/ELF radio waves and to reconstruct the wave energy distribution nicely at the ionospheric base. Secondly, the Bayesian information criterion is shown efficient and very promising to handle the situations where the data number is too small compared to the number of unknowns which is the case of most reconstruction problems.