Effect of alignment methods on liquid crystal performance in millimeter wave devices

Abstract

We investigate the effect of different alignment methods on the performance of dual frequency liquid crystal-based phase shifters operating at 30 GHz to determine the optimal alignment method for such devices. We measure the response time, total phase shift and repeatability of devices with the liquid crystal alignment created by a rubbed polyimide alignment layer deposited on the metallization elements, devices with the alignment created by direct rubbing of the metallization elements, and devices with no initial treatment for alignment. For these tests, we used a commercial, dual frequency liquid crystal. We find that the devices with a polyimide alignment layer in an anti-parallel rubbing orientation produce the best results; however, the other devices produce acceptable results due to the nature of the dual frequency liquid crystal and they may be alternatives to polyimide in certain applications.