Effective dielectric constant of top grounded coplanar waveguide on liquid crystal superstrate

The effective dielectric constant of the top grounded coplanar waveguide with a liquid crystal (LC) superstrate for phase shifting applications is investigated in the frequency range of 30-60 GHz. Two nematic LC mixtures, namely E7 and MDA-00-3506, are used as the superstrate. The measurements show that MDA-00-3506 offers higher values of phase shift per millimeter than its E7 counterpart. In particular, the MDA-00-3506 provides 3.14°/mm, whereas E7 gives 2.79°/mm at 60 GHz. The results of the dielectric constants from measurement and computer modeling are found to agree to within 5%. For the modeling, a comprehensive finite element package predicting the local alignment of LC molecules and effective dielectric constant at different bias voltages and frequencies are used. Copyright © 2013 Wiley Periodicals, Inc.