Application of liquid crystal technology for electronically scanned reflectarrays

Electronically steerable antenna systems are required for many applications including communication systems and radar. Normally these employ diode phase shifters to create the required aperture distribution. In this paper we show how the anisotropy property of liquid crystal (LC) material can be exploited to provide an integrated phase shifter for a printed patch antenna such as a reflectarray (N. Misran et al., 2003). This offers a simpler alternative to semiconductor devices and has the potential to overcome the limitations of existing phase shifter technology in the millimeter and submillimeter wave bands. In this paper we demonstrate the relationship between the LC thickness and the attainable phase range for a patch element in which the change in LC permittivity can be obtained by applying a dc voltage between the patch conductor and the ground plane. Simulations for different LC substrate thicknesses were carried out using the transmission line model (TLM) MICROSTRIPES and the finite element model (FEM) Ansoft HFSS. Measurements the scattering parameters of a 200 μm and a 500 μm thick patch reflectarray have been performed using waveguide simulator technique to demonstrate the validity of the predictions.