Optimizing Isolation in Interleaved Co-Frequency Orthogonally Polarized Circular Patch Array Antennas Using Conformal Mantle Cloaks and Integrated Decoupling Patches

Employing two closely spaced arrays operating at the same frequency with orthogonal polarizations and independent operations present significant potential for miniaturizing telecommunication systems. This paper presents two interleaved, tightly spaced circular patch array antennas that operate at the same frequency but with orthogonal polarizations. The arrays are arranged in the E-plane, with one array rotated 90 degrees to achieve orthogonal polarization—Array-I is x-polarized, while Array-II is y-polarized. This configuration provides both spatial and polarization diversity, which helps reduce signal degradation caused by multipath fading and enhances overall channel capacity. However, the inherent symmetry of the circular patches typically results in significant coupling between adjacent arrays when they are closely spaced, which can severely degrade antenna performance. In this study, we investigate the effectiveness of conformal mantle cloaks and decoupling patches in isolating two interleaved co-frequency circular patch array antennas. Our designed mantle cloak, composed of a conformal substrate with parallel metallic strips, successfully eliminates cross-coupling between adjacent elements in the interleaved arrays, although it does not fully mitigate inter-element coupling within each array. To further address this issue, we employ small patches with shorting pins to minimize mutual coupling among the elements of each array. These isolating techniques enable minimal proximity between the arrays, achieving a center-to-center spacing of 28.88 mm (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.54\lambda _{0}$ </tex-math></inline-formula>) and an edge-to-edge gap of less than 1 mm (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{0}$ </tex-math></inline-formula>/50), theoretically approaching zero at the resonant frequency of 5.6 GHz. The conformal substrate of the cloak, produced using 3D printing technology, simplifies the fabrication process by covering only the top surface of the patches. The proposed design has been successfully fabricated and evaluated using detailed comparison metrics, including return loss, mutual coupling, radiation patterns, gain, and efficiency across cloaked and uncloaked configurations. The simulation and experimental results closely match, confirming that the cloaked antennas exhibit similar radiation performance to isolated elements.