Influence of design liquid crystal-based devices on the agility capability

Abstract

This article deals with liquid-crystal-based tunable components: phase-shifters and patch-antennas. It reports on investigations about the influence of design on their characteristics. For phase-shifters based on an inverted microstrip line, the line design is paramount for improvement of phase-shift and Figure-Of-Merit. Moreover, the use of liquid crystal in the design of patch antennas allows adjustment of the resonance frequency, and slot insertion results in size reduction with no decrease of performances. Both cases highlight the interest of liquid crystal in millimeter frequency devices.

Effect of polyimide layers on the permittivity tuning range of liquid crystals

“…The two microstrip lines on both sides of the top layer patch are connected to SMA connectors to enable measurements of the transmission and reflection coefficients. The standard liquid crystal K15 [9] was used for filling the cavity of this resonator element. The values of perpendicular and parallel permittivity for this material are presented in Table I.…”

A Liquid-Crystal, Tunable, Ultra-Thin Fabry-Perot Resonator in Ka Band

“…The molecules can be aligned using either an external electric/ magnetic field or a mechanical effect based on a spin-coated and rubbed specific surface treatment layer with a polyvinylalcohol (PVA) solution. In this case, to guarantee a minimum agility, the thickness of the LC layer should be kept as thin as possible [26], [27].…”

Liquid Crystal Tunable Filter Based On DBR Topology

“…K15 and BL037 (Merck). A frequency characterization of both LCs from 1 to 26 GHz was reported in [7]. Table 1 gives the dielectric constant and losses at 5 GHz.…”

“…Table 1 gives the dielectric constant and losses at 5 GHz. One should note that this technology was previously used in other circuits such as phase-shifters and antennas [7] and led to promising results. It consists of three elements: a copper-made ground plane, a cavity containing the LC and a substrate with the designed filter.…”

“…Reports are available in the literature about investigations carried out on the use of LCs to achieve planar phase shifters [4]- [6]. Recently, LCs have been implemented in other planar electronic functions such as antennas [7], delay line [8], or waveguide [9].…”