A Low‐Profile Circularly Polarized Antenna Array With Considerable Overlapped Impedance and Axial‐Ratio Bandwidths for 5G N78 Band

ABSTRACT A compact, low‐profile circularly polarized (CP) antenna element is proposed using a two‐layer printed circuit board (PCB) configuration. The radiator on the top of the first PCB is a rectangular loop inside with four sector‐shaped patches, excited by a cross‐slot of the ground on the top of the second PCB. The cross‐slot is fed with a Γ‐shaped microstrip line on the bottom of the second PCB. Based on this designed method, two CP modes are formed. The measured results show that it has a −10 dB impedance bandwidth (IBW) of 3.23–3.84 GHz (17.26%) and a 3 dB axial‐ratio bandwidth (ARBW) of 3.33–3.71 GHz (10.80%), a realized gain of 7.70 ± 0.10 dBi and an average radiation efficiency of 72.56% over ARBW. Furthermore, a 2 × 2 antenna array is constructed using the proposed element and a four‐way toroidal power divider network. The array is fabricated and measured with a −15 dB IBW of 3.20–3.94 GHz (20.73%), an ARBW of 3.16–3.96 GHz (22.47%), and a realized gain of 12.05 ± 0.19 dBi over 3.3–3.8 GHz band. Therefore, the left‐handed CP array demonstrates that it can be a promising candidate for the 5G n78 systems.