94 GHz printed reflectors using C-shape patches

Folded printed Fresnel zone plate reflector is presented for helicopter collision avoidance radar at 94 GHz. The achievement of a folded structure, requires printed elements that perform a 180deg phase difference of the reflected phase between two orthogonal polarizations. For this purpose, C-shape patches were designed. A prototype of 130 mm diameter was made and measured. The first section describes the reflector design with a focus on the C-shape patches mode of operation. The second part shows the concept validation by the mean of antenna´s radiation pattern measurements as well as in flight measurements of the antenna mounted on the detection radar.