A Review on high gain slotted waveguide arrays in different planar configurations

Planar waveguide slot arrays (WSAs) have been employed as early as the 1940s and are now widely applied as reliable antennas in high-frequency systems, with significant use in communication and RADAR systems. This work offers a thorough survey of the most frequently discussed waveguide slot array configurations, with particular focus on their main shortcomings and constraints, as well as potential effective solutions. Our focus has been primarily on the advanced design techniques available to achieve high-performance WSAs. The review contains WSAs that are partially filled and those overlaid with single or multiple dielectric layers. Additionally, we introduce and accurately model the most significant second-order effects present in the feeding network of planar arrays. A particular focus is directed toward the T-junction responsible for feeding the array and the interaction phenomena between each slot coupler in the feeding network and the adjacent radiating slots, as well as the impact of waveguide bends. These factors can greatly increase the first sidelobes relative to the ideal case, resulting in a significant reduction in the array's overall performance