A Broadband Wide-Beam Circularly Polarized Antenna Array for Urban Macrocell Base Stations

An eight-element broadband wide-beam circularly polarized (CP) antenna array is developed for mobile wireless communications. The CP antenna element consists of two rectangular loops with gaps for circular polarization and parasitic elements for bandwidth enhancement. A wide beamwidth is achieved in the horizontal plane because the CP antenna elements have a narrow cross section in the plane. The CP antenna array also has higher isolation between antenna elements than a linear polarized (LP) array with the same element space, which is due to the polarization mismatch caused by the currents in the CP antenna elements. The eight-element CP antenna array achieves a bandwidth of 40% (1.7-2.55 GHz) for return loss >15 dB and a bandwidth of 47% (1.67-2.7 GHz) for axial ratio (AR) <; 3 dB. The half-power beamwidth and the 3 dB AR beamwidth in the horizontal plane are ~65° ± 8° and approximately 100°, respectively. The antenna gain for the array is about 17 dBi. The CP antenna array is suitable for applications in urban macrocell base stations.