Electrodynamic analysis of a ring array of log-periodic vibrator antennas over flat rectangular perfectly conductive surface

When building mobile radioelectronic complexes, the issues of developing antenna systems that provide high indicators of spatial-frequency selectivity of signal transmission and reception become important. Ring arrays of log-periodic vibrator antennas are used for all-round view of space in wide range of working frequencies. The similarity of the ring structure when rotating around the central axis by an angular distance between the elements allows you to maintain a high directivity within 360°. Design of logarithmic-periodic receiving-emitting components in the form of a set of vibrators, the length and location of which vary according to a logarithmic law, enables to preserve identical conditions for exciting scale-invariant fragments when changing the operating wavelength. Rational methods of analyzing antenna systems on carriers are based on constructing electrodynamic models of their receiving-emitting structures when located on objects, according to electrophysical properties, profile and size corresponding to fragments of real carrier surfaces. The purpose of the article is to study patterns of antenna array directional pattern changes in the wavelength range when placed above the screen. A system of integral equations for calculation of currents in approximation of models of wire vibrators and an infinitely thin flat plate with rectilinear boundaries has been obtained in the interests of studying characteristics of a ring array of log-periodic vibrator antennae placed above a flat perfectly conducting screen of resonant electrical dimensions. To take into account electromagnetic connections in the array and electromagnetic interaction with the underlying surface through secondary electromagnetic radiation when setting the boundary value, boundary conditions have been applied to the superposition of electric fields on electric vibrators from the composition of log-periodic antennas and the plate. Currents have been found by the results of partial inversion of the operators of integral equations in the form of a set discrete values providing restoration of their distributions at controlled execution errors of boundary conditions of boundary value problem. Calculated values of complex amplitudes of currents have been used for calculation and regularities of antenna array directional pattern change in the range of operating wave-lengths have been revealed. It has been shown that presence of the screen leads to an increase in the level of the side lobes of the antenna beam pattern relative to values characteristic of free space. At the same time, the shape of the directional pattern of the log-periodic vibrator antenna undergoes the greatest transformation, the axis of which is oriented perpendicular to the edge of the screen. Improved spatial frequency selectivity of signal transmission/reception has been achieved by increasing the height of the array and the size of the underlying surface due to a reduction in the intensity of secondary radiation created by surface currents reflected from the edges. The shapes of the main beams of the directional patterns of log periodic antennas are mainly determined by the values of the aperture angles and periods of the structure. They undergo minor distortions when expanding the active areas due to the guidance of currents on the vibrators by the secondary electromagnetic radiation of the screen. Based on the electrodynamic analysis of the ring array of log-periodic antennas above the perfectly conductive screen with rectilinear boundaries, the relationship of its directional pattern with the design parameters has been established. Obtained results make it possible to substantiate technical appearance of range receiving-emitting structures for mobile radioelectronic complexes at circular view of space in wide band of working wavelengths.