140-GHz High-Efficiency Low-Profile Reflectarray Antenna Using Heterogeneous Design Strategy

A novel planar heterogeneous design strategy of a reflectarray antenna (RA) from the perspective of an equivalent medium is presented. A weak resonance criterion for constructing and selecting elements is proposed accordingly. Three types of weak resonance heterogeneous elements and element libraries are constructed to achieve fully continuous phase shift and low loss, which further contribute to realizing high-efficiency RA. To validate the design strategy, high-efficiency low-profile RAs using LTCC technology are designed for demonstration. The measured results indicate the heterogeneous RA achieves a maximum aperture efficiency of 46.32% and a high gain of 31.40 dBi at 140 GHz. Compared with conventional homogeneous RA, the maximum aperture efficiency is improved by 11%. The proposed high-efficiency low-profile RAs are promising candidates for short-distance communication in sub-millimeter wave and terahertz (THz) bands.