Mutual Coupling Analysis of Open-Ended Ridge and Ridge Gap Waveguide Radiating Elements in an Infinite Array Environment

In this paper, we discuss mutual coupling effects in 2-D beam-steerable antenna arrays based on open-ended ridge and ridge gap waveguide radiating elements. Considering potential applications for beyond-5G systems in W-/D-band, the radiating elements are designed full-metal realizing a high radiation efficiency. Various decoupling structures based on electromagnetic soft surfaces are applied to suppress the surface waves over the array apertures. The infinite array approach is used to analyze antenna unit cells in an isosceles triangular lattice, which results in the active reflection coefficient over a scan and frequency range. The latter is used to extract the values of the mutual coupling coefficients between the elements. The analysis demonstrates the effect of decoupling structures realizing a steep drop of the mutual coupling magnitude (≤ − 20 dB) for closely-spaced array elements. This results in a wideband (≥ 20%) and wide-scan (> 50°) element beam-steering performance.