A Dual-Polarized Multi-Wideband Ceiling Antenna With Eight-Diagram Shape for 2G/3G/LTE/5G Sub-6 GHz Indoor Applications

This paper presents a dual-polarized, multi-wideband ceiling antenna with an eight-diagram shape for indoor communication in the 2G/3G/LTE/5G sub-6 GHz frequency range. The horizontally polarized (HP) antenna element consists of an upper frequency eight-diagram shaped radiation element and a lower frequency ring-shaped dipole radiation array, both are printed on one side of a printed-circuit-board (PCB). These elements are fed by a pair of different 1-to-4 power divider (PD) networks on the other side of the PCB. The HP antenna elements are connected by a wideband diplexer and fixed by four nylon columns, ensuring wide bandwidth and good isolation. Additionally, the vertically-polarized (VP) antenna element is positioned at the center of the lower-frequency HP dipole radiation array and consists of two orthogonal conical patches with an open groove. This configuration allows for wide frequency bandwidth, high gain, and aesthetic characteristics. Measurement results demonstrate a wide impedance bandwidth of 114.3% (1.5-5.5 GHz) in the VP direction, as well as two bandwidths of 78.6% (1.66-3.81 GHz) and 8.5% (4.75-5.17 GHz) in the HP direction for the 2G/3G/LTE/5G sub-6 GHz bands. The corresponding peak gains vary within 1.06-6.09 dBi and 3.65-4.95 dBi, respectively. Furthermore, the port isolation level between the HP and VP elements reaches 25 dB, demonstrating satisfactory performance for practical ceiling applications.