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.

Eight-element liquid crystal based 32 GHz phased array antenna with improved time response

“…The use of DFLC in microwave device both with and without alignment layers has recently been discussed [33]. The use of an alignment layer in a standard nematic LC is critical as the alignment layer governs the response of the LC and provides an orientation for the LC to relax to when the voltage is removed.…”

New quasiperiodic structures in nematic liquid crystals

“…[5][6][7][8][9] Since the discovery of domain walls, topological defects have become a robust field of LC research, with extensive reviews, [10][11][12][13] in addition to the expansive field of LC display applications. [14][15][16][17][18][19][20][21][22][23] Domain walls have been shown to reduce into a pair of disclination lines at a critical field strength, in the pincement process. 24 Newer experiments and theoretical work have reported on velocity of the front to expand the knowledge of this phenomena.…”

Vertically Stacked Soliton‐Like Domain Walls in Nematic Liquid Crystals

“…[4] This tunable difference is used in optical display technology and other applications, including optical filters and tunable microwave devices. [5][6][7][8][9] Dual-frequency nematic LCs share the same properties as ordinary nematic LCs, but they are also tunable with the frequency of the biasing voltage. This can improve the transition speed of LC devices and permit the additional tuning of the dielectric anisotropy to create a tunable filter.…”