Abstract

Extremely high frequencies used in future wireless communication systems such as 6G require low loss materials to avoid wasting power and maintain acceptable efficiency. Furthermore, especially in the internet of things (IoT) applications, low weight and the possibility to focus the radiation pattern in the desired direction would also improve the communication between units and reduce the required signal power. Radio frequency (RF) lenses for signal focusing can be made from low loss and low relative permittivity materials. In this work, the development of sustainable composites with a relative permittivity of ∼1.15 and loss tangents in the range of 10⁻³ is presented. The composites were fabricated at the exceptionally low temperature of 95 °C and were based on hollow micron-sized glass spheres and three different types of cellulose nanofibers as the water-soluble binder. A simple manufacturing method through casting and drying is presented. The surface properties of the composites were investigated with surface profile analysis and the dielectric properties by SPDR and terahertz spectroscopy. The weight of the fabricated lens was 0.6 g and the transmittance was 99.85%. The lens improved the antenna gain by 14–18 dBi depending on the surface smoothening. Also, coating the lens with a moisture protecting agent did not alter the lens performance.