Design and analysis of a continuously linear polarization agile antenna using microwave liquid crystal technology

Abstract

This paper presents the design and analysis of a continuously linear polarization-agile antenna based on Microwave Liquid Crystal (LC) technology. The proposed concept is specifically developed for Ku-band (e.g. 12 GHz) satellite communication applications, where systems typically operate with linear polarization and maintaining polarization alignment, referred to as skew angle adjustment, is critical for reliable on-the-move operation and for avoiding link loss. The antenna system incorporates a tunable feed network comprising two directional couplers and LC-based continuously tunable phase shifters. These feed a dual-fed microstrip patch antenna, enabling full-range linear polarization control over +/- 180 degrees by electronically adjusting the differential phase. The proposed tunable feed network is implemented using microwave LC technology to enable a fully passive architecture without requiring low-noise amplifiers. LC materials offer electrically tunable dielectric properties with inherently low dielectric loss, typically below 0.06 at frequencies beyond 10 GHz, and their loss tangent decreases with increasing frequency, making them particularly well-suited for Ku-band applications and beyond. In addition, LC materials benefit from a mature fabrication infrastructure originating from LC display manufacturing, allowing low-cost, large-area, and scalable production. Full-wave simulations at 12 GHz show that the system achieves a cross-polarization discrimination (XPD) better than 25 dB across the entire skew angle range. The LC-based phase shifters operate with only two bias voltages and provide 180 degrees differential phase shift with an insertion loss below 2.3 dB, yielding a figure-of-merit of 80 degrees/dB at 12 GHz. These results demonstrate the feasibility of the proposed design for low-loss, scalable, and reconfigurable antenna arrays in Ku-band and beyond satellite systems.