A Low-Profile Dual-Band Self-Decoupled Shared-Aperture Patch Antenna Array for 6G Beamforming

This paper presents a dual-band shared-aperture patch antenna array with self-decoupling capability. A patch unit is first proposed, comprising four square patches and a Jerusalem cross-shaped stripe (JS), all located on the same PCB layer. The unit operates in the high-band (HB) mode by individually exciting any of the four patches, and in the low-band (LB) mode by exciting the central JS, which in turn excites the entire unit. The two operating bands exhibit a small frequency ratio of 1.2:1, enabling coverage of adjacent 6G mid-bands. Both in-band and cross-band isolations exceed 20 dB across all ports, without requiring additional decoupling structures. To demonstrate scalability, four units are cascaded to form a larger array. Small T-shaped stripes, also printed on the same layer, are introduced to enhance isolation between HB patches nested in different units, while the units maintain self-decoupling in the LB. Both the patch unit and the array are fabricated and tested. The measured results agree well with simulations, validating the proposed design. The array operates in two bands: the LB centered at 12 GHz with an 14.2% bandwidth, and the HB centered at 14.5 GHz with a 11% bandwidth. Beam-scanning ranges of ±50° in the HB mode and ±20° in the LB mode are achieved. With its structural simplicity, low profile, self-decoupling capability within both bands, and robust beamforming performance, the proposed array serves as a promising phased array candidate for future 6G applications.