Dual-Band Decoupling Between Extremely Closely Spaced PIFAs Based on LC Resonator

In this article, we propose a simple scheme for dual-band antenna decoupling utilizing parallel LC resonators. By leveraging the common mode and differential mode (CM/DM) S-parameters, we provide a convenient method for distinguishing the coupling characteristics between the antennas. Based on this approach, we show that the dual-band PIFAs operating in the TM_0,0.5 and TM_1,0.5 modes exhibit electric and magnetic coupling (E/M coupling) in the respective frequency bands. The decoupling of these two bands can be achieved in a methodological way using the inductance of the parallel LC resonator below the resonant frequency and the capacitance above the resonant frequency. Decoupling for different frequency ratios can be readily adjusted by modifying the impedance characteristics of the LC resonator. By controlling the relative positions of the LC resonators, separate adjustments of decoupling in the two bands can be accomplished, thereby simplifying the decoupling process. To validate the effectiveness of the proposed method, a prototype is fabricated. The measured results demonstrated that the proposed scheme achieves effective isolation enhancement from 5 to 14 dB and 9 to 15 dB in two frequency bands, respectively. The proposed decoupling scheme offers a simple and efficient decoupling process with an easily realizable structure, making it a promising solution for future multi-input multi-output (MIMO) system designs.