Time-domain free-space evaluations of urethane slabs with finite-difference time-domain computer simulations

This paper describes the extraction of electrical material properties of lossy, carbon-doped urethane slabs using a free-space time-domain reflectivity measurement system developed by the National Institute of Standards and Technology. In order to validate the measurement results. The measurement system was simulated using the finite-difference time-domain method. Reflectivity measurement results and theoretical predictions as a function of carbon-doping, frequency, and angle of incidence are presented. Excellent agreement is obtained between measured and simulated results. Finally, complex permittivity results are presented for two urethane slabs with different carbon-doping levels, and the dispersion is a strong function of the amount of carbon.