Angle-Dependent Synthesis Method for Holographic Multi-Feed Antennas

Abstract

A novel synthesis method for holographic multi-feed antennas is presented to combine all sub-holograms into an angle-dependent shared holographic aperture. In order to find the global error minimum between the shared holographic aperture and all ideal sub-holograms, a non-pixel-based genetic optimization is used. For a more accurately implementation of the analytical impedance tensor an eigenvector approach taking all tensor components into account is introduced. The optimized holographic antenna has four feeds for an exemplary integration into a 2D-monopulse radar system and is realized on a fused silica wafer due to its lower loss at millimeter-wave frequencies compared to Teflon-based materials. The antenna prototype provides a measured gain of 23 dBi, a polarization purity of 26and a side-lobe level of 20for feed 1, 2 and 4 is reached across 76–81. The S-parameters are measured from 60to 90, and a reflection coefficient of –14and an inter-port coupling <–38are achieved. The measured 2D-monopulse patterns provide a FOV of 10, the sum beam has a gain of 26 dBi leading to an aperture efficiency of 45and the differential beams show a null depth of 30.