Wideband Radiation Pattern and Port Decoupling Method for E- and H-Plane Linear Arrays

For the first time, a propagating mode cancellation method is proposed for wideband radiation pattern and port decoupling in semi-open waveguide. Metallic vias and strips can be used to suppress the fundamental TM^z and TE^z modes of the semi-open waveguide, respectively. By tuning the decoupling structure, the forward propagating wave can be largely canceled and therefore a standing wave is formed. This cancellation effectively confines the electromagnetic energy within each antenna element, enabling wideband radiation pattern decoupling and high port isolation. Based on propagating mode, this technique is inherently broadband. To verify the proposed method, two 1 × 8 multiple-input multiple-output antenna arrays operating are designed, fabricated, and measured for both E- and H-plane configurations. The measured overlapping bandwidths are 10.8% and 9.7% for the E- and H-plane arrays, respectively, with isolation levels higher than 20 dB. Furthermore, stable and uniform radiation patterns are consistently maintained across these bands, with the maximum radiation direction along the boresight direction. © 2026 IEEE.