A 2 to 16 GHz dual polarized end fire ETS array with corrugated edges for unified ECC evaluation framework

This paper presents a reusable evaluation framework for broadband dual-linearly polarized end-fire multiple-input-multiple-output (MIMO) arrays based on exponentially tapered slot (ETS) elements. A 2 × 2 ETS subarray operating from 2 to 16 GHz is used as a case study, where three representative edge treatments are compared: a double-sided corrugated edge (Double-CE), a single-sided corrugated edge (Single-CE), and a bare aperture without corrugation. Under unified port reference planes and a common spherical sampling grid, the framework jointly examines S-parameters, 2D/3D radiation patterns, axial-ratio/circular-component descriptors (as auxiliary polarization indicators), and pattern-based envelope correlation coefficient (ECC). Simulated results indicate that all three strategies achieve broadband impedance matching and maintain low inter-port coupling over most of the 2-16 GHz span under the unified reference configuration, while localized resonant features in coupling and correlation are sensitive to the intra-subarray pitch. The end-fire main beam is preserved at representative frequencies, with mid-band peak realized gains on the order of 9-10 dBi. Pattern-based ECC (Port 1-Port 2) further reveals a frequency- and pitch-dependent isolation-correlation trade-off: Double-CE produces the smoothest radiation envelope and a more uniform multiport environment at the nominal layout, but high-ECC cases can emerge at specific nodes when the pitch is perturbed toward tighter spacing; Single-CE can achieve very low correlation at selected mid-band nodes (e.g., around 8.02 GHz) and provides a favorable trade-off under appropriate pitch settings, whereas elevated ECC may still occur at other nodes. Surface-current snapshots link these metric-level trends to boundary-mediated current channels, edge scattering, and cavity-mode participation, providing practical guidance on choosing symmetric versus intentionally asymmetric edge loading. Although demonstrated on a specific ETS topology, the proposed framework is directly extendable to other end-fire array elements, subarray layouts, and boundary treatments for broadband MIMO applications.