Pattern-Reconfigurable Dipole Antenna Based on Odd- and Even-Mode Principle for 5G-NR Communications

A novel planar pattern-reconfigurable dipole antenna with three unidirectional radiation patterns based on the odd- and even-modes is proposed. One of the dipoles operates on the fundamental mode (odd-mode), and the other works on the high-order mode (even-mode). They are tightly combined in space and fed by a microstrip line placed at the axis of symmetry. By ingeniously introducing small strips, the dipoles can be series-fed in the center with in-phase/out-of-phase shifting, thereby reducing the number of feeding ports. The positive and negative excitations of the strip-loaded dipole are controlled by two PIN diodes. Consequently, the relative phase of the even-odd-mode and the beams could be reconfigured. In addition, a switch-controlled director is added to enhance the gain of the endfire pattern and enhance the overlapping impedance bandwidth of all states. The fabricated antenna features a compact size of $0.46\lambda _{0} \times 0.28\lambda _{0} \times 0.009\lambda _{0}$ ( $\lambda _{0}$ represents the free-space wavelength at 3.50 GHz). The measured overlapped bandwidth reaches 15.3% (3.26–3.80 GHz) with $\vert {S}_{11}\vert \lt -10$ dB. The measured peak gain and radiation efficiency of the proposed unidirectional pattern diversity antenna exceed 3.70 dBi and 71% in the operating frequency band, respectively. The proposed antenna is well-suitable for intelligent 5G-NR N78 band (3.30–3.80 GHz) communication systems.