Liquid crystal varactor loaded variable phase shifter for integrated, compact, and fast beamsteering antenna systems

This paper presents a microstrip variable delay line loaded with liquid crystal varactors in series. The design of the device, including both the theoretical analysis and the fabrication, is presented. The proposed design shows a high LC varactor tuning efficiency of 83% and a low response time in the order of 3 seconds. These high performances result from implementing the varactors in parallel plate capacitor topology and with a 10 μm thick LC layer as a tunable dielectric between the electrodes. Simulation and measurement results verify that a designed prototype can provide a differential phase shift of 60° at 20 GHz with an insertion loss no higher than 2 dB.