Broadband Dielectric Characterization of High-Permittivity Rogers Substrates via Terahertz Time-Domain Spectroscopy in Reflection Mode

We report the dielectric characterization of three commercially available, high-permittivity Rogers laminates in the sub-terahertz range, by means of terahertz time-domain spectroscopy measurements in reflection mode. A transmission-line model is developed to obtain the reflectance spectra as a function of the frequency-dispersive complex relative permittivity of the substrates. The latter is fitted through optimization to a single Lorentzian term, which is shown to accurately reproduce the measured reflectance spectra. The substrates RO3010 and RT/duroid 6010.2LM exhibit significant frequency dispersion of both their relative permittivity and loss tangent. Conversely, the thermoset microwave laminate TMM10i is characterized by both a lower frequency dispersion and overall dielectric losses, thus making it a promising candidate for the design of low-profile and broadband components for novel terahertz applications. Owing to the simple Lorentzian dispersion model used for the description of the relative permittivity, the presented results can serve as a reference, and they can be directly introduced in design and optimization workflows for novel devices in emerging terahertz applications.