Synthesis of a travelling wave slotted substrate integrated waveguide (SIW) array with dual-circular polarization

SIW slot array antennas fed by emulated waveguide feed structure have lower insertion loss when compared to planar printed antennas. They are easy to manufacture, have light weight, and their use should lead to a lower cost fabrication as well. A synthesis procedure for the SIW antenna design is introduced, where the optimum slot parameters and the number of slots per radiating SIW can be optimized for a given beam tilt angle. Slots are designed to provide specific coupling factors that are determined numerically using an approximate step-by-step design recipe. The coupling is a function of slots dimensions, slots spacing, and beam tilt angle. A full array prototype with 32 radiating SIW guides with 13 "X" shaped slots, and a folded feed network have been developed. The feed network of this multi-layer slot array has been tapered to maximize the antenna efficiency and lower the side lobe level.