Metal Rod-Based Field Concentrated Common and Differential Modes Theory Enabling Design of Dual-Polarized Antennas

This article introduces a logical design approach, grounded in an updated understanding of common mode (CM) and differential mode (DM) theory, for the development of dual-polarized antennas operating in the sub-6-GHz N78 band (3.3–3.8 GHz). Our method entails a sophisticated design process that uses the field concentration to achieve the condition of the mode segmentation of
${S}$
-parameters. Notably, enhanced port isolation between the two orthogonal polarizations is accomplished by employing independently controllable Smith chart traces for each mode, utilizing intuitive techniques based on loading metal rods. To offer a comprehensive understanding of the underlying mechanisms that enable the dual-polarized antenna’s realization, we present the associated field distributions derived from the CM and DM analyses. The suggested antenna has undergone simulation, fabrication, and measurement processes. Both simulated and experimental findings demonstrate that the antenna can achieve the maximum isolation of 40 dB, an 8-dBi gain, 35-dB cross-polarization discrimination, 90% efficiency with stable radiation patterns, and a
$0.14\lambda _{0}$
profile throughout the 3.3–3.8-GHz range employing cost-effective FR-4 substrates. Moreover, this study contributes a design methodology for dual-polarized antennas, as well as furnishing the active
$S$
-parameters for a comprehensive range of amplitude and phase sequences to represent realistic situations accurately.