This technology relates to the development of liquid crystal reflectarrays for eliminating communication obstacles (coverage holes) caused by building shadows and other obstacles in high-frequency wireless communications after 5G. The “two-directional electric field drive method”, which applies electric fields in the vertical and horizontal directions to the liquid crystal layer, makes it possible to control the orientation of the liquid crystal molecules in a fast and stable manner. This overcomes the response delay of thick liquid crystals, which has been a problem in the past, and enables control of the direction of radio wave reflection in the millimeter wave band.

Conventional reflective arrays include a high-speed control method using varactor diodes and a simple-structured method using liquid crystal, but each has its own problems. In particular, the response delay (several seconds to several tens of seconds) caused by the thick layer of the liquid crystal method was a problem. In this technology, stripe-shaped electrodes are added to the liquid crystal layer to apply electric fields from both vertical and horizontal directions, and the response time has been successfully reduced to 500 ms or less.

• The most distinctive feature of this technology is the high-speed response control of liquid crystal molecules by means of bidirectional electric field drive. This makes it possible to drive even thick liquid crystal layers at low voltages (30 V or lower), and enables almost natural responsiveness for video display and communication control. We have also established a design guideline that maximizes dielectric constant change by optimizing the electrode structure, utilizing simulation technology for liquid crystal orientation.

This technology is applicable to radio wave control in the millimeter and terahertz bands, and is expected to be deployed in reflectarrays, phased array antennas, variable delay lines, and beam formers. We will continue to optimize the liquid crystal materials and electrode structures, and through evaluation of actual millimeter-wave reflection characteristics, we aim to implement this technology in telecommunication infrastructures.