Radiation properties of microwave reflector antennas covered with a water film

Using simple models, first-order effects of a thin water film over the reflector surfaces of symmetrically fed microwave reflector antennas on the antenna radiation pattern and cross-polarisation in the frequency range 10¿15 GHz are investigated. It is shown that the influence of the water film on cross-polarisation and the main-mode radiation pattern can usually be neglected, but that the minimum in the tracking mode can be substantially deteriorated. In addition, it was found that, in the frequency range 11¿15 GHz, under certain circumstances the antenna gain can be reduced by as much as between 1 and 2 dB.