Design and fabrication of 3D-printed high gain broadband Fresnel zone lens using hybrid groove-perforation method for millimeter-wave applications

This letter presents a novel hybrid design approach for the Fresnel zone lenses (FZL). The method combines the two conventional design approaches: grooved and perforated methods. Perforated lenses minimize the shadow blockage that grooved lenses suffer from, and therefore provide improved antenna gain. However, the fabrication of the low refractive index regions in the perforated lenses is challenging due to the limited manufacturing resolution, which means low refractive index dielectrics cannot be realized. The proposed hybrid FZL design utilizes the perforated method for the inner regions and applies the grooved method for the outer regions. This paper describes the equations used to optimize the design and gives the general design guidelines. A hybrid FZL antenna that operates at the center frequency of 33 GHz is presented. Measurement results show that the hybrid FZL improved the realized gain by up to 3.2 dB and the -3 dB gain bandwidth by up to 2 GHz when compared with the equivalent grooved FZL.