Tsai, Chung-EnChung-EnTsaiLin, Yi-ChengYi-ChengLin2026-04-242026-04-242025-12-0815223965https://www.scopus.com/record/display.uri?eid=2-s2.0-105030865572&origin=resultslisthttps://scholars.lib.ntu.edu.tw/handle/123456789/737506The paper presents the compact design of a co-existed dual circularly polarized (DCP) antenna element and its sequentially rotated 2 × 2 arrays. The design is realized by integrating two opposite sequentially rotated feeding networks and four DCP antenna elements, all co-located in a compact shared aperture. The entire arrays are fed by dual ports, denoted as Port 1 and Port 2 for the right-hand circular polarization (RHCP) and the left-hand circular polarization (LHCP), respectively. By sharing the co-existed DCP antenna elements and stacked feeding networks, the entire arrays may reduce the radiated aperture and overall size. The feeding networks use sequential rotated schemes to generate a successive 90-degree phase delay for RHCP and LHCP antenna ports. Simulated results demonstrate an impedance bandwidth exceeding 25% and a 3-dB axial ratio bandwidth with a worst case of 27%. Radiation performance exhibits decent peak gains of 10 dB and 8.5 dB at 12 GHz for the right-hand and the left-hand circular polarizations, respectively. The proposed compact co-located design is successfully realized and verified through the simulated stable radiation patterns of dual circular polarization.falseconference paper10.1109/ap-s/cnc-usnc-ursi55537.2025.112662272-s2.0-105030865572