A Liquid Crystal Tunable Metamaterial Unit Cell for Dynamic Metasurface Antennas

This communication presents a liquid crystal (LC)-based electronically tunable metamaterial unit cell that can serve as a building block for dynamic metasurface antennas (DMAs). The metamaterial unit cell was designed based on a complementary electric-inductive-capacitive (cELC) resonator, whose structure was modified into double metal layers for ease of loading the LC mixture. The equivalent capacitance, and thus the transmission coefficient of the metamaterial unit cell, can be tuned by external biasing voltages. The metamaterial unit cell couples to the transverse magnetic (TM) field, making it easy to be embedded into waveguide-fed structures such as microstrip lines or parallel-plate waveguides. In addition, it is individually addressable, which meets the design requirement of DMAs. Experimental results show that the transmission coefficient of the metamaterial unit cell can be continuously tuned from -2.7 to -6.5 dB at 29 GHz with a biasing voltage swinging from 2.5 to 10 Vrms. The response times are around 150 ms for both switch-ON and swtich-OFF cases.