Influence of the feed location on the performance of a conformed Fresnel zone reflector

This letter investigates the effect of varying the feed position along the focal axis on the performance of a conformed Fresnel zone reflector. Bandwidth and aperture efficiency are analyzed by illuminating the proposed reflector antenna with a pyramidal horn at Ku band. The antenna under study is a new type of Fresnel zone plate antenna that, compared to the conventional parabolic reflectors, has the benefits of flat profile and small weight. In comparison to reflectarrays, conformed Fresnel zone reflectors present lower losses and are easier to fabricate. An offset-fed square reflector of 40 × 40 cm² was designed and analyzed, providing 26% of 1.5-dB gain-bandwidth and 55% of aperture efficiency. Numerical results show that modifying the feed position leads to a remarkable shift in operating frequency band. Therefore, the proposed design offers the possibility of changing the operating band by moving the feed without redesigning the entire antenna. Also, a notable increase in gain is observed when the feed is moved away from the center of the antenna.