Broadband complex permittivity measurement of paraffin films at 26 GHz–1 THz using time domain spectroscopy

In this work, we report complex permittivity measurement of thick paraffin films at the frequency range of 26 GHz-1 THz. Paraffin is a low loss dielectric polymer that exhibits a 15% volumetric change through its solid-liquid phase change. Unique electrical and mechanical properties of paraffin makes it an attractive phase change material for the development of millimeter wave (mmW) and terahertz (THz) reconfigurable RF components such as variable capacitors and antennas. We employ a free-space measurement technique using time domain spectroscopy (TDS). Complex permittivity of paraffin is characterized over the frequency range of 26 GHz-1 THz by using Debye relaxation model to extrapolate the measurement data for lower frequencies. Measured relative permittivity of paraffin is 2.26 and loss tangent is measured to be 1.57 × 10^-4 at 26 GHz and 0.006 at 1 THz.