Electrically Tuned Microwave Devices Using Liquid Crystal Technology

Abstract

An overview of liquid crystal technology for microwave and millimeter-wave frequencies is presented. The potential of liquid crystals as reconfigurable materials arises from their ability for continuous tuning with low power consumption, transparency, and possible integration with printed and flexible circuit technologies. This paper describes physical theory and fundamental electrical properties arising from the anisotropy of liquid crystals and overviews selected realized liquid crystal devices, throughout four main categories: resonators and filters, phase shifters and delay lines, antennas, and, finally, frequency-selective surfaces and metamaterials.

Liquid crystal enabled substrate integrated waveguide variable phase shifter for millimeter-wave application at 60ghz and beyond

“…Principle o f the Permittivity Tuning o f Le Materials As explained in the literature [6], [7] and [10], the nematic LC bulk usually has all its rod shaped molecules in random orientations as shown in Fig. l They de fine an effective permittivity Geff and an effective loss tangent tanoeff with respect to the electric field vector of a RF signal therethrough.…”

Nano-Objects and Ions in Liquid Crystals: Ion Trapping Effect and Related Phenomena

“…Their numerous applications include displays and E-books, tunable filters and lenses for applied optics and biomedicine (hyper spectral imaging, ophthalmology), polarization control devices (tunable wave-plates, retarders, rotators, polarization generators), and components in optical processing systems (spatial light modulators and optical light valves). They are also used in adaptive optics, lasers, holography, optical communications (beam steering devices and optical waveguides), microwave technologies (tunable delay lines, phase shifters, antennas), and countless other areas [1][2][3][4][5][6][7]. Typically, commercial devices based on molecular liquid crystals are driven by an electric field.…”

Design of X-band reconfigurable frequency selective surface with high isolation

“…These techniques have the advantage of being able to reconfigure frequencies in a wide frequency range from the RF bandwidth to the optical frequency bandwidth by changing the properties of a material. However, these techniques also have the disadvantage of being very sensitive to the surrounding temperature and humidity, making it difficult to correct for the desired operation [10,13].…”