High-Gain MIMO Dipole Antennas With Mechanical Steerable Main Beam for 5G Small Cell

A dipole antenna with a bent dumbbell shape was positioned above and horizontal to a metal reflector to improve peak gain and steering of the radiation pattern. A parasitic square patch etched on the bottom side of the dumbbell arms provided a feeding delay line for producing dipole radiation in the 3600 MHz band. For gain enhancement and beam reconfiguration, the height of the horizontal dipole and the metal reflector could be adjusted to generate constructive reflections in phase with the radiated waves. When a dipole antenna with a height equal to half a wavelength was installed above the metal reflector, it exhibited a tilted main beam of 48° and maximum gain reached 9.2 dBi. A multiple-input-multiple-output antenna with a pair of strip stubs was also investigated. Simulation and measurement results indicated that the proposed structure achieved good isolation. The antenna had an impedance bandwidth (VSWR ≤ 2) of approximately 19.0% (3146-3818 MHz) and a low coupling (S21) of less than -25 dB. In this band, the average gain enhancement approximated 5.1 dBi.