V.А. Kuznetsov – Ph.D. (Eng.), Senior Lecturer,

MTSC Air Forces «MAA named professor N.E. Zhukovsky and Y.A. Gagarin» (Voronezh) E-mail: kuzzviktor@mail.ru

D.V. Ambrosov – Adjunct,

MTSC Air Forces «MAA named professor N.E. Zhukovsky and Y.A. Gagarin» (Voronezh) E-mail: dmitryambrosov@mail.ru

Currently, air target radar cross section (RCS) estimation is one of the key and to the end unsolved problems in radar. The process of obtaining radar information about an air target in full-scale and physical experiments is very difficult, because of considerable economic and time costs. Therefore, it is proposed to use mathematical modeling as the most accessible way to obtain information about the characteristics of an air target reverse secondary radiation. At present, there is a possibility of a fairly accurate mathematical description of the air target surface using graphic editors, for example, by the well-known plastic (facet) method based on approximation of the object's surface by elementary sections (triangles or square plates). The complex facet model synthesized in this way allows to take into account the electromagnetic characteristics of each facet. When calculating the air target RCS, it is also necessary to take into account that secondary sources of stray electromagnetic fields distributed on the complex faceted model surface describing an air target, make sense only on those surface areas that are visible from the receiving and transmitting active phased array antenna air-based radar. So, the choice of the visibility checking algorithm is one of the most important factors in air target complex faceted model RCS evaluating, which affect the accuracy of the calculations.

To date, the following algorithms are most often used in radar when air targets faceted models RCS evaluating: shading and masking, facets visibility checking by the angle between the nor-mal vectors and the direction of irradiation, algorithms based on the calculation of triangle intersection points. In spite of the fairly high accuracy of most of them, large computational resources are required to models facets visibility checking. The results of the time costs evaluation at the quantitative and qualitative levels made it possible to substantiate the impossibility of applying the existing algorithms in real time. In the work, in order to reduce of facets vertices coordinate matrix size, it was proposed the transition to the dotted surface description of a complex object. In this case, the centers of mass of facets are considered as points. To check the visibility of three-dimensional objects, the surface of which is given by points, it is proposed to use the HPR algorithm, first used to solve the tasks of the air targets RCS evaluating. However, when solving problems of this class, it is required to take into account the orientation of the reflecting surface relative to the point of irradiation. Therefore, it is offered to combine the proposed approach with the known algorithm for sampling visible facets by the angle between the normal vectors and the direction of irradiation. This will increase the reliability of the facets visibility checking results in the air targets models RCS evaluating tasks.

The results of the research of the algorithms considered in the work showed that the pro-posed combination of them is optimal according to the criteria of maximum processing speed and high reliability. In addition, a criterion has been formulated for choosing the HPR algorithm optimal parameter lg(R), which allows minimizing the error in determining the visibility of complex object surface points. With this in mind, the HPR algorithm can be considered as optimal by the criterion of the minimum of the facets visibility checking error, and when averaging the optimal parameter lg(R) over all observation conditions of the air target, as quasi-optimal. The application of a new approach to sampling visible surface points of the model reduced the processing time for a large facets vertices coordinates array, which suggests that it can be used to target RCS evaluating when solving problems of modeling their radar portraits in the dynamics of air combat in real time.

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