Mutual Coupling Reduction for Linearly and Circularly Polarized Electromagnetic Wave Based on Miniaturized Absorptive Metamaterial

In this paper, an absorptive metamaterial unit cell consisting of a round microstrip line with four lumped elements loaded at the midpoint of each side is proposed. This unit cell, exhibiting central symmetry and being polarization-insensitive to incident waves, is ideally suited for capturing circularly polarized waves within its resonance frequency band. In contrast to the majority of previous research that focused on large-scale metamaterial structures, this paper introduces a novel approach aimed at miniaturizing the metamaterial while preserving its exceptional absorption characteristics. By simplifying the periodic boundary of the metamaterial cell unit, a one-dimensional absorptive metamaterial comprising merely four unit cells is introduced between two closely spaced microstrip antennas. A comprehensive numerical analysis is conducted, examining the coupling coefficient, impedance matching, and radiation characteristics under both linearly and circularly polarized scenarios. The simulation results reveal that the presence of this absorptive metamaterial effectively suppresses mutual coupling by over 27 dB, while simultaneously enhancing impedance matching and optimizing the axial ratio (AR).