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 mum, 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 t_off are as low as 4 ms.     

Tunable liquid crystal phase shifter for microwave frequencies

A tunable phase shifter using liquid crystal (LC) is presented. The device is fabricated in a fashion similar to LC displays which makes fabrication very simple compared, for example, to MEMS approaches. At the targeted operation frequency of 20 GHz the device offers a performance of above 60 differential phase shift per dB insertion loss and a minimum tuning speed of 340 ms.