Liquid crystals (LCs) have developed from pure electro-optic (E-O) display materials towards the functional media for reconfigurable microwave and millimetre wave (MMW) antenna systems. This is mainly possible with systems which have electrically controllable dielectric anisotropy ( \(\Delta \varepsilon\) ) that facilitates tuning of effective permittivity continuously. This tunability permits dynamic adjustment of resonant frequency, phase response, polarization state and radiation pattern without mechanical actuation or high power semiconductor switches. The present paper comprehensively reviews the application of LCs in antenna technologies, including frequency-agile arrays, frequency-reconfigurable microstrip patches, polarization-agile arrays, reflectarrays (RAs), folded RAs, phased arrays, leaky-wave antennas, metasurfaces, flexible liquid crystal polymer (LCP) based wearable antennas, low voltage systems and optically tunable platforms. In the reviewed results, tuning of frequency ranges between 7–18% over MMW bands, beam steering as high as ± 60°, phase shifts goes beyond 300°, reflectarray (RA) gain is up to 25 dBi and wearable 5G systems have low voltages of 0.4–0.6 V. Furthermore, these systems span frequency of operation between 3 and 78 GHz with a variety of LC material strategies and alignment. However, despite these advancements, challenges such as dielectric loss ( \(tan\delta\) ≈ 0.01–0.03), limited response time, temperature sensitivity and alignment precision remain critical constraints. Therefore, future research is directed towards developing high anisotropy, low loss LC mixtures, faster switching mechanisms, improved metasurface integration and scalable transparent or flexible architectures to enable adaptive, energy efficient platforms for next generation 5G/6G, satellite and Internet-of-Things (IoT) communication systems.
