46-57

UDC 621.396
DOI: 10.15350/2306-2819.2018.4.46

DEVELOPMENT THEORY OF FOCUSED ANTENNAS FOR THE TASKS OF ACOUSTIC ECHOLOCATION DIAGNOSIS

Yu. E. Sedelnikov, M. N. Kachushkin, D. A. Vedenkin
Kazan National Research Technical University named after A. N. Tupolev (KNRTU-KAI),
10, K. Marx Street, Kazan, 420111, Russian Federation
E-mail: miihon@bk.ru

ABSTRACT

Introduction. Currently, the progress, achieved in acoustic echolocation, allows to develop systems that effectively maintain focusing of the transmitted or received fields. This applies both to the use of real arrays with weakly directional antennas and virtual arrays that implement the principle of coherent integration of signals received at different points in time and space. The use of focusing provides the perspectives for improving detection efficiency that is substantial for small-sized defects. The aim of the research is to acquaint specialists in antenna focusing with poorly studied properties of focused systems. The paper discusses the general properties of focused systems and their major features as well as presents the comparison of characteristics of a continuous antenna and antenna array. A comparison of the distribution of the near-field and far-field zones in the region of the focal point is presented. Paper thoroughly describes the following models: spatial distribution of the field intensity in the focal plane parallel to the aperture; the intensity distribution of the vertical field component in the focal plane (parallel and perpendicular to the aperture); the intensity distribution of the horizontal field component in the focal plane parallel to the aperture. There is presented the features of the directivity in the Fresnel zone including: limited value in comparison with the far zone; attenuation, depending on the interferences in the propagation medium as well as on the focal length; nonuniformity of directivity distribution in comparison with the far zone. The dependences of the size of the focal region and side lobes for the near-field zone are presented. The most substantial aperture qualitative properties are described for the cases of focusing a transmitted or received field toward the transverse direction along the aperture symmetry axis. Conclusions. For practical applications, these properties open new perspectives for improving the equipment for echolocation diagnostics. Some of them have already been proposed, the other ones seem potentially promising, however require further studies.

KEYWORDS

acoustic; focused systems; echolocation diagnostics; Fresnel zone; focal region

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ACKNOWLEDGMENT

This work was supported by the grant № 8.6872.2017/БЧ from the Ministry of Education and Science of the Russian Federation.

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For citation: Sedelnikov Yu. E., Kachushkin M. N., Vedenkin D. A. Development Theory of Focused Antennas for the Tasks of Acoustic Echolocation Diagnosis. Vestnik of Volga State University of Technology. Ser.: Radio Engineering and Infocommunication Systems. 2018. No 4 (40). Pp. 46-57. DOI: 10.15350/2306-2819.2018.4.46