A direction‐finding algorithm of reflected waves using small‐sized data series measured in fresnel region and its evaluation

To find the unwanted reflection characteristics of a Fresnel region wave from a building and a wall, it is necessary to know the direction of the reflection source. This paper proposes an algorithm which estimates successively the direction of arrival of the reflected wave in the Fresnel region, based on the study of the characteristics and the shape of the spatial series in that region. This algorithm is realized by a combination of the maximum entropy method in which a spectrum can be estimated at a high resolution with a few data and an error correction by the Newton‐Raphson method for solution of a nonlinear equation. To confirm the validity, a computer simulation and experimental results are shown. In the computer simulation results, the reflection direction was estimated with an error of 0.1° ‐ 2.9° from 40 measured data for an aperture of 5 wavelengths. In the experiment, the reflection direction was estimated with an error of less than 0.5°. From these results, it is found that this algorithm can be applied for direction finding of the reflected wave under an actual electromagnetic environment.