A Single-Layer Six-Element Patch Array With Rotationally Symmetric Layout and Dual Decoupling Lines for Beidou Navigation System

Due to the complicated coupling mechanism and strict axial ratio (AR) requirement, decoupling circularly polarized (CP) patch arrays are essential for satellite navigation systems. In this article, a six-element CP array with a rotationally symmetric layout is designed for the Beidou navigation system. The coupling mechanism between CP array elements is intuitively revealed using the orthogonal mode decomposition (OMD) method. In this way, the mutual coupling can be characterized by two coupled modes: a spatial coupled mode (SCM) and a ground coupled mode (GCM). Furthermore, coplanar dual decoupling lines with very compact sizes are proposed for decoupling the adjacent array elements. The SCM and GCM are simultaneously suppressed by the novel structure. Consequently, the isolation between adjacent CP array elements is improved from 12.5 to 45 dB. Benefiting from the improvement of isolation, the realized gain of the CP array element is improved from 2.0 to 4.1 dBic, and the AR is also improved from 2.6 to 1.6 dB. Moreover, the decoupling structures can be placed on the same layer of the patch elements. Such a single-layer design has low-cost and low-profile merits, which is potentially useful for various satellite navigation systems.