Terahertz Modal Analysis of a Grounded Liquid-crystal Cell and Its Application as a Tunable Cavity Antenna

The complex mode spectra of a grounded anisotropic dielectric slab (GADS) excited by a horizontal magnetic dipole are presented in the low THz range. A liquid crystal mixture with high birefringence, low dispersive behavior and moderate losses at THz frequencies is selected as anisotropic layer. The dispersion curves of the complex modes (in both the surface-wave and leaky-wave regime) supported by the GADS are compared to those supported by the equivalent isotropic grounded dielectric slab GDS with the ordinary and the extraordinary components of the liquid crystal permittivity tensor. The modal analysis of the GADS is then performed for different values of the bias voltage to show the potential dynamic control of the phase and attenuation constant. The proposed study constitutes an approximate yet solid background for the design of THz leaky-wave antennas and suggests the feasibility of THz planar antennas with a tunable pointing angle.