Design of Frequency-Reconfigurable and Decoupled Dual-Port Single-Radiating Patch Antennas Using Characteristic Mode Analysis

In this article, a novel frequency-reconfigurable and decoupled method for dual-port single-radiating patch antennas is proposed. This method is implemented by field and circuit investigations using characteristic mode analysis (CMA). First, the resonant frequencies and modal electric fields of even and odd modes are studied in detail by loading single-column metallized vias on a single-radiating patch. The coupling between two ports is suppressed by even and odd mode cancellation. Then, the gap capacitance is introduced by etching slots on both sides of the metalized vias on the single-radiating patch. The capacitance varies with the length of the slots. Subsequently, two p-i-n diodes are implanted in each slot, and the length of the slots is adjusted by controlling the on-off state of the diodes, thereby tuning the resonant frequency of the modes. Equivalent circuit models are employed to further delve into the decoupling mechanism and guide the selection of inductance and capacitance. Finally, frequency-reconfigurable and decoupled antenna (FRDA) is elaborately designed and fabricated, and good agreement is achieved between the simulation and the measurement. The measured broadband tuning and significant isolation performances validate the effectiveness of the proposed method.