Measurement-based Characterization and Application of Low-Loss Dielectric Materials for Development of 6G Sub-THz Antennas

The development of high-frequency components for future 6G sub-terahertz (THz) systems is a challenging task, partly because of extremely high signal losses at sub-THz frequencies. This includes intra-system and inter-system losses. One way to overcome intra-system losses is to use packaging materials with smaller loss tangents (Df) for the development of 6G components. To overcome inter-system losses, high gain antennas and efficient power amplifiers are required to increase the equivalent isotropic radiated power (EIRP). However, these amplifiers generate heat, which may cause the values of the relative dielectric constant (Dk) and Df of the material to change with temperature. This change in Dk and Df values may degrade the performance of antennas and other components integrated in the vicinity of the amplifiers. Therefore, low-loss materials whose Dk and Df values do not fluctuate significantly with temperature are required for future 6G systems. In this paper, we present and illustrate methods for accurate extraction of the Dk and Df values of packaging materials at sub-THz frequencies, considering a low-loss Ajinomoto Build-up Film® (ABF) material as an example. The Dk and Df values of the non-metallized and metallized ABF material were extracted in the 140 GHz band using the Fabry-Pérot and planar resonator methods, respectively. Furthermore, temperature-dependent Dk and Df values of the ABF material were also extracted up to 100°C. Our results reveal that the Dk and Df values of this material are stable over a wide range of temperatures. Finally, we used the characterized low-loss ABF material to develop a 6G sub-THz antenna array. The 1x5 elements series-fed U-slot patch antenna array was designed, fabricated and measured in the 140 GHz band. A large impedance bandwidth and high peak gain of approximately 15 GHz and 12 dBi respectively, were measured. Excellent correlation was obtained between measurement and simulation results.