A simple method is proposed for the realisation of compact dual-polarised antennas. The aperture area of a dual-polarised dipole antenna can be reduced by half by surrounding the antenna with a square loop. Based on the method, a broadband compact dualpolarised antenna is developed. The broadband dual-polarised antenna consists of two �45°-polarised dipoles surrounded by a square loop and fed by two orthogonal broadband baluns. A resonance at a sfrequency ( f Lr = 0.7 GHz) is created by the square loop, leading to a compact size of about λ Lr /4 � λ Lr /4, where λ Lr is the wavelength in free space at f Lr . Another resonance at a higher frequency ( f Hr = 1.5 GHz) is generated by etching open slots on the �45°-polarised dipoles. A combination of the lowerfrequency and the higher-frequency resonances results in a broadband operation. Simulation and experimental results show that the compact dual-polarised antenna achieves an impedance bandwidth of 75% (0.69-1.52 GHz) for return loss > 15 dB with stable radiation patterns, which is potential to be used for 5G new radio base-station applications.
K E Y W O R D S broadband antennas, dipole antennas
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An ultra-wideband dual-polarized antenna with a low profile is proposed for base-station applications. The dual-polarized antenna consists of two crossed dipoles, a square patch, and a square meta-surface. The ultra-wideband operation is achieved by the coupling between the crossed dipoles and the square patch which creates multiple resonances. The square meta-surface is introduced atop the antenna to improve the impedance matching. It is shown by simulation and experiment that the dual-polarized antenna achieves an impedance bandwidth of 76.5% over 2.3 to 5.15 GHz for voltage standing wave ratio (VSWR)<1.5, covering the frequency bands for long term evolution LTE-2300/2500 and 5G new radio (NR) sub-6G n7/n38/n41/ n77/n78/n79 systems. The ultra-wideband antenna features stable radiation patterns with a gain of 8.5 ± 0.5 dBi and a half-power beam width (HPBW) of 65°± 5°.
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