Split-Ring Slot in the Broad-Wall of a Rectangular Waveguide

Recently the Slotted Waveguide Antenna Stiffened Structure (SWASS) was introduced, where an antenna array is incorporated as an integrated part of a load bearing structure. The array element spacing and individual radiating element sizes play a critical role in the overall mechanical strength of the structure. These parameters are constrained by Slotted Waveguide Antenna (SWA) array design, and the coupling of the waveguide electromagnetic fields to the radiating apertures. In this letter, the radiation characteristics of a split-ring slot in the broad-wall of a rectangular waveguide are investigated for the first time. The simulated and measured results show that the split-ring slot radiates a linearly polarized wave with a total efficiency and realized gain close to those of conventional rectangular slots. The proposed split-ring slot has an outer diameter of 0.186 λ₀, a significant size reduction compared to a traditional 0.5 λ₀ rectangular slot and the previous limit of 0.25 λ₀ for metamaterial loaded rectangular slots. The reduced aperture size of the split-ring slot alleviates the impact of the radiating elements on the mechanical strength of the structure.