Liquid crystal-based beam switchable three-element microstrip parasitic array

A liquid crystal (LC)-based three-element microstrip parasitic array with beam switching is presented in this study. To understand the beam switching mechanism, a simple theoretical model of three-element Yagi antenna on the ground is given and analysed. In the proposed microstrip parasitic array, LC permittivities under three elements can be adjusted by bias voltages to control their resonant electrical lengths. In the tuning process, the LC-based antenna array can operate at three modes to obtain three beam switching directions. The measured results show that three beam tilt directions (θ = 59°, −2°, −57°) in the H-plane are achieved.