Abstract :
The Fresnel zone plate reflector antenna takes the form of a flat plate, yet offers similar focusing properties to the conventional parabolic dish. To improve the antenna performance, phase correcting techniques must be used. One successful approach is to employ the multi-layered structure. A novel zone plate reflector with a single phase correcting metallic layer is presented. By covering different sub-zones with uniformly distributed resonators of different dimensions, the phase correction required by an ideal zone plate is approximately provided, thus yielding a high efficiency zone plate reflector. As an experimental prototype, a microwave quarter-wave zone plate reflector was fabricated. A phase reversing zone plate reflector of the same dimension served as a reference. In order to reduce the aperture blockage, a helical antenna was employed as the feed. Experiments showed that both reflectors have about 12% 3 dB bandwidth. In the operating band, the new reflector has an average of 2 dB gain increase. The phase correcting mechanism makes the main beam narrower and sidelobes lower, and a 11 dB improvement in interference rejection is obtained at +or-8 degrees .
