Adaptive circular polarization

Circular polarization is a radar technique which is commonly employed to reduce the relative precipitation echoes which make it difficult to detect small aircraft. The basic principles of this technique are briefly examined. When a radar transmits a circularly polarized electromagnetic wave, the receive aperture will not respond to the reflections from spherical objects if the transmit and receive apertures have the same 'sense' of polarization. Approaches for improving the considered technique are considered, taking into account the effects of differential attenuation, drop deformation, and multipath.