Liquid-crystal varactors with fast switching times for microwave applications

A varactor using liquid crystal (LC) as tunable dielectric is presented. The two devices described feature LC layer thicknesses of 5 and 1 mm, respectively. A more advanced fabrication scheme is used, which incorporates the use of fused silica as the LC enclosing substrate. The devices exhibit tunabilities of at least 18% and quality factors of at least 40 at 1 GHz. The switching times toff are as low as 4 ms.