Fast Reconfigurable Phase Shifter Based on a Chiral Liquid Crystal Configuration
Dowon Kim, Kitae Kim, Mohsin Hassan Saeed, Sehwan Choi, Jun‐Hee Na
Abstract
Liquid crystals (LCs) offer a promising playground for developing reconfigurable radio frequency devices due to their unique dielectric properties, including large birefringence and tunability. Previous research on reconfigurable phase shifters has primarily focused on studying loss, response, and tunability. However, the influence of surface-enforced alignment on LC remains an area that requires further exploration. Here, we designed a phase shifter using twisted nematic aligned cells. To characterize the phase-shifting behavior of the nematic LC, we employed the transmission line method within the frequency range of 5 to 8 GHz and extracted the dynamic electrical parameters. Numerical simulations based on finite element methods were conducted to predict the alignment of LC molecules and the propagation of waves within the test cell. The phase shifter achieved a phase difference of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim $ </tex-math></inline-formula> 220° by applying a bias voltage to the LC. In particular, we compare the dynamic response of the phase shifter and a twisted LC configuration having a chiral dopant that responds 10 times faster than the homogeneous mode.