K.K. Klionovski

New applications of global positioning systems GLONASS and GPS require significant improvements in the characteristics of the equipment users, in particular, the antennas system of radio navigation receiver. The antenna system consists of an antenna element and the ground plane, which is designed to reduce positioning errors caused by the effect of multipath signal. One of the trends in the development of GNSS antenna systems is to create ground planes, providing a decrease of reception the reflected signals at low elevation angles to the plane of the ground plane θe. At low angles can be understood as a range from 0○ to 50○. For such purposes, may use a semi-transparent ground plane, which is characterized by the fact that on the surface of the ground plane at the same time does not equal zero reflection coefficient and transmission coefficient of the incident electromagnetic wave. The paper carried out theoretical and experimental research of round semi-transparent ground planes with uneven impedances distribution on the surface of the ground planes. Phase of impedance is inductive. The three-dimensional diffraction of external source as a ring of magnetic current with a standing wave relatively to the azimuthal coordinate on a semi-transparent disk is considered. The external source in the form of a ring current with a standing wave can simulate directional antenna, such as a patch antenna, as well as to consider the directional characteristics of the structure for E-and H-plane. Unknown electric current of ground plane is determined by numerically solving the integral equation by method of moments. Theoretical and experimental radiation pattern and DU ratio of antenna with a semi-transparent ground plane at the frequencies of GPS L1 (1586 MHz), GPS L2 (1236 MHz) and GPS L5 (1176 MHz) are presented in comparison with the conductive ground plane of the same size. The effect of impedance's phase distribution on the DU ratio is investigated.