Beam Steering by Liquid Crystal Based Leaky Wave Antennas

An original liquid crystal (LC)-based substrate integrated waveguide (SIW) leaky-wave antenna (LWA) is proposed. Inside the SIW, there is an embedded strip line sandwiched between an LC pool and another dielectric slab. The antenna couples the guided quasi-TEM mode into free space through a periodic set of complementary electric inductive-capacitive (cELC) resonators. Simulation results show that the antenna performs fixed-frequency continuous beam steering of 52 degrees from backward -28 to forward 24 degrees at 25.85 GHz. This relatively wide beam scan angle is achieved by tuning the LC permittivity through an applied quasi-DC bias voltage to the strip line. Simulation results show that the antenna has high realized gain through the entire scanning range (less than 1 dB degradation), relatively wide bandwidth, and good tolerance to frequency drift and fabrication errors. We also present a reconfigurable one dimensional LWA in the terahertz region. The proposed LWA can steer its beam at a fixed operational frequency using LC. It consists of a rectangular waveguide filled with three layers of dielectric: an LC layer sandwiched between two spacers. The dominant TE10 mode leaks into the free space through a partially reflecting surface (PRS). Using numerical analysis, we optimized the PRS reactance and the LC ratio for maximum gain and beam steering angle and confirmed the results by full-wave simulation.