V.M. Vladimirov, V.V. Markov, Yu.L. Fateev, V.N. Shepov

Accuracy characteristics of active patch slot leaky wave antennas with the right-hand circular polarization with the ground plane diameter of 175 mm and 80 mm have been studied. It has been shown that miniaturized antenna has a more stable phase center, better ellipticity and higher level of the cross-polarization suppression in the upper hemisphere of the received navigation signals. However, with the antenna diameter decreasing, the increase of the cross-polarization level in the lower hemi-sphere results in the miniaturized antenna being less resistant to multipath interference which is the main source of the high-accuracy positioning errors. For example, with the active antenna diameter decreasing from 175 mm to 80 mm the root-mean-square deviation (RMSD) of the positioning error of an antenna relative to the others increases from 2,1 to 3,9 mm in the horizontal plane, and it increases from 1,7 to 3 mm in the vertical plane. RMSD of the positioning accuracy at the azimuth angle increases from 6,12 to 12,5 (angular minutes), at the roll angle from 9,4 to 15,6 (angular minutes), at the pitch angle from 6,85 to 19,5 (angular minutes), with the distance between the centers of the three antennas being 0,7 m. It should be noted that these results have been obtained for the active antennas with the small-size ground planes. Such antennas are designed for being used in transport. Therefore, to resist the multipath interference in the considered antennas the main attention is paid to the characteristics of the antennas themselves. To apply the given antennas in stationary GLONASS/GPS base stations it is possible to further suppress multipath interference using ground screens of special design, for example, a conventional choke ring screen or a low-profile impedance screen with a varying impedance.