RADIO ENGINEERING, cilt.84, sa.9, ss.26-39, 2020 (Diğer Kurumların Hakemli Dergileri)
In subsurface radar, the monostatic principle of registration of radar data is successfully applied, in which the transceiver module of the radar moves with a certain step along the flat surface of the object being examined and measures the amplitude and phase of the field at different frequencies ... The module can be moved either by the operator or using a two-dimensional scanner. A significant disadvantage of a radar with a scanning transceiver module is its low performance. To increase it, various antenna arrays can be used: either linear antenna arrays, scanning along the perpendicular axis, or fixed two-dimensional antenna arrays. To ensure the required quality of the received microwave images, the space between adjacent elements in the antenna array should not exceed a quarter of the wavelength of the sounding signal, therefore, with a wavelength of several centimeters, typical for the subsurface radars under consideration, the number of elements in the antenna array turns out to be quite large, which significantly increases the cost of the radar. The problem of reducing the number of elements in the antenna system of a subsurface radar can be solved by using a multistatic method, where sparse transmitting and receiving antenna arrays operating on the MIMO (Multiple Input - Multiple Output) principle are used. The multistatic principle of an antenna system is that when a signal is emitted by each transmitting element, the reflected signal is recorded not by a paired receiving element, as in monostatic radar, but by all receiving elements. Thus, the number of independent received field samples is equal to the product of the number of transmitting elements by the number of receiving elements. This raises the question of their optimal positioning. This paper proposes a method for designing multistatic antenna systems of subsurface radars. The method consists in obtaining the optimal parameters of the transmitting and receiving antenna arrays with an equidistant arrangement of elements by solving the optimization problem of minimizing the objective function, which characterizes the quality of the microwave image of a set of point objects uniformly distributed within the surveyed area. Several variants of the objective function are considered: 1) characterizing the degree of focusing of the microwave image of a set of point objects; 2) characterizing the uniformity of the microwave image of a set of point objects; 3) a combination of the first and second variants with different weights. It is shown that the best results are obtained using the first variant of the objective function. It is also shown that the proposed approach provides higher quality of microwave images than the existing approach of equivalent virtual elements.