Low-cost Fresnel Zone Plate Lens Antennas for Millimeter-wave and Terahertz Applications

Description

Due to demands from consumer markets in personal communications, security andautomotive safety at millimeter waves on the one hand and new promising applicationsof Terahertz in explosive detection, tomographic imaging of transdermal drug delivery,and cultural heritage conservation, etc., on the other, we embark on investigating a keysystem component in millimeter-wave and terahertz antennas. At these frequencies, thelow power available necessitates the use of high-gain antennas such as Fresnel zoneplate (FZP) lens antennas.Albeit their large electrical size, FZP lens antennas have been investigated for manyyears due to their planar geometry and ease of fabrication at microwave frequencies.While the physical size of the FZP lens antennas is small at millimeter waves andterahertz, simple frequency scaling alone would not lead to cost-effective designs asstandardized fabrication processes have tolerance limitations and substrate materials areonly commercially available for specific electrical properties and thicknesses. Workingwith these two constraints, we have successfully completed a GRF project entitled “AnInvestigation of High-Order Mode Microstrip Antennas for 60 GHz Short-RangeWireless Communications,” in which low-cost 60 GHz magneto-electric dipole antennaswere fabricated with 0.787mm Duroid 5880 substrate using plated through hole (PTH)and printed circuit board (PCB) techniques. In this project, we propose to investigate theapplicability of these low-cost fabrication techniques for FZP lens antennas with equalE- and H-plane radiation patterns and enhanced gain. The former is realized by aninnovative PCB feed design based on the complementary source approach while thelatter is achieved by removing part of the substrate materials in the in-phase regionsand/or applying periodic slot patterning on the out-of-phase printed ring regions.Our preliminary results, using 0.254mm Duroid 5880 substrates and mechanically drilledPTH vias with a diameter of 0.1mm, achieved 26dBi for a 10-ring FZP lens at 0.3 THz.Simulation, fabrication and testing of the preliminary designs were all conducted inhouse in the State Key Laboratory of Millimeter Waves (Hong Kong). We willinvestigate the frequency limit of the proposed low-cost approach before we resort toother conventional lithographical techniques for our quest of high-gain FZP lensantennas up to 1 THz which is limited by our measurement facilities.We strongly believe that the proposed research will contribute to the development ofcritical components for THz technology using low-cost materials and PCB and PTHtechnologies that Hong Kong electronic industry has mastered and perfected.