Over-the-horizon Ka band radio wave propagation studies in the coastal South Australian Spencer Gulf region

Anomalous propagation of microwave and mmW (millimetre Wave) radiation in the surface boundary layer due to the changing gradients in the refractivity height profile surface can significantly enhance, or degrade, the performance of mmW radio receiver systems. Although propagation under anomalous conditions has been modeled, the dependence of accurate refractivity profiling on pressure temperature and moisture means that the validation of models relies on coordinating measurement of these parameters with tropospheric radio link and radar experiments. A height-distributed multi-element transmit-receive 35 GHz CW carrier radio link over 26 km has been built and operated in trials in the Spencer Gulf concurrently with atmospheric refractivity profiling instrumentation that provides a full description of the tropospheric conditions over the air/sea interface. This paper describes an analysis of received signal strengths associated with a low-height evaporative ducting structure that was present during a daytime recording period. Modeling of the observed reception has been conducted with a parabolic equation approach. Radio wave reception measurements at heights above the sea surface ducting structure are consistent with the presence of a stable refractivity profile.