Compact TM10/TM20 Mode-Switchable Patch Antenna for Beam Diversity

A compact patch antenna capable of beam diversity is proposed based on switchable $\mathbf{T M}_{\mathbf{1 0}}$ and $\mathbf{T M}_{\mathbf{2 0}}$ modes. The antenna employs a dual-port configuration, achieving two distinct radiation patterns-broadside and dual tilted beams-through inphase and out-of-phase excitations, respectively. Unlike many reconfigurable designs that rely on active components such as RF switches, this design eliminates the need for such elements, thereby significantly reducing design complexity, implementation cost, and power loss. To address the inherent frequency gap between the $\mathbf{T M}_{\mathbf{1 0}}$ and $\mathbf{T M}_{\mathbf{2 0}}$ modes, which typically resonates at a $\mathbf{2: 1}$ ratio, two central slots and a set of shorting pins are integrated into the patch. These structural features effectively compress the two modal frequencies into a common operating band. Furthermore, the shorting pins serve a dual function by facilitating impedance tuning, thus optimized matching for both excitation conditions. The antenna maintains high-gain performance in each mode and provides a passive, efficient, and structurally simple solution for beam control in systems requiring radiation pattern adaptability without compromising efficiency or reliability.