Dual-polarized Patch Antenna of Large Frequency Tuning Range at mm-Wave Frequency Bands

In this paper, we present a dual-polarized frequency-reconfigurable patch antenna working at millimeter wave frequency bands for 5G applications. A square patch is surrounded by four metallic L-shaped walls. Four ideal varactor diodes are placed between the corners of the square patch and L-shaped walls. Frequency tunability is achieved by adjusting the capacitances of the varactor diodes. Two 50-Ω probes are used to feed the square patch which can excite two orthogonal polarizations. Operating frequency can vary from 23 GHz to 45 GHz with a 10-dB return loss when the capacitance decreases from 0.05 pF to 0.005 pF. The isolation between two polarizations is better than 13 dB over the operating frequency bands. Cross-polarization level is lower than −15 dB. In addition, the quality factor of varactor diodes is studied to demonstrate its influence on antenna efficiency.