Investigation of coupling based on liquid crystal in two end-coupled microstrip resonators

A new tunable planar coupled resonator structure based on nematic liquid crystals (LC) substrate for applications at mm-wave frequencies is presented. The proposed structure allows the use of electric field bias to align the LC molecules, offering direct control over the dielectric properties (anisotropy) of the LC substrate. The structure is designed for use of a LC mixture commonly referred to as E7. Symmetrical and asymmetrical couplings are investigated using this coupled resonator structure. In both cases, coupling tunability of about 20% is achieved in the 30 - 40 GHz range. The proposed structure can also be exploited to realize miniaturized tunable filters with wide tuning range at mm-wave frequencies.