Isolation Enhancement for Wideband, Circularly/Dual-Polarized, High-Density Patch Arrays Using Planar Parasitic Resonators

A planar double-layer hybrid decoupling structure with the polarization-insensitive characteristics is proposed as an effective isolator for wideband, circularly/dual-polarized, high-density patch arrays. The hybrid decoupling structure is composed of two types of resonators, i.e., an H-shaped structure on the lower layer and a couple of meander lines on the upper layer. By integrating the decoupling structure into the dual-polarized array and circularly polarized array, respectively, the mutual coupling between the antenna elements is significantly reduced. In detail, the isolation levels between the co-polarization (co-pol) ports in dual-polarized array are improved by ~9.40 dB and the port isolation level in circularly polarized (CP) array is improved by ~12.7 dB, while the inter-element center-to-center distances are as low as 0.5 λ₀. Good agreement between the simulated results and the measured results is obtained.