Modeling and Design of High Isolation Dual-Polarized Aperture-Coupled Microstrip Patch Antennas with Dual-Offset Feedlines

In this paper, the steps required to model and design high isolation dual-polarized aperture-coupled microstrip patch (ACMP) antennas with dual-offset feedlines are presented. The proposed approach requires that the effective impedance of the antenna when fed in a balanced mode be determined as a function of the distance between the dual-offset feedlines. Equations relating the effective impedance with the feed geometry are derived from experiments, enabling the design of matching networks for any given effective impedance. This study shows that ACMP antennas with dual-offset feedlines can be matched to the source using $\lambda / 4$ transformers and T -junctions. A 10 GHz dualpolarized antenna with dual-offset feedlines was designed and simulated in an electromagnetic solver using the proposed methodology. A return loss of 20.6 dB in port 1,51.1 dB return loss in port 2,75.5 dB of isolation between excitation ports, and crosspolarization levels below 60 dB at broadside were achieved.