This paper suggests the antenna diversity combining technique for synchronized pseudolite system to overcome a periodic signal null effect caused by the sea surface specula reflection. The diversity is of important when location of pseudolite is nearby sea coast in inevitable reasons, because it degrades the continuity and time synchronization performance of the system. In this paper multipath characteristics by the sea surface are investigated briefly and then two combining methods (i.e. the equal gain combining and the switched combining) are considered for receiver design and compared in terms of the diversity gain and the SNR null depth. Simulation results show that both of two combining methods prevent the null effect in the Fresnel zone well, but there was no notable difference between two methods (e.g. 1 dB) when two antennas are considered.

Keywords: diversity combining, pseudolite, Sea surface multipath, fresnel zone