Microwave detection of rubber filler using rectangular dielectric waveguide

This paper highlights the design and development of a nondestructive measurement system for detecting the percentage of carbon black using rectangular dielectric waveguide (RDWG) measurement system. The rubber composite of various percentages of carbon black is sandwiched between poly-tetra-fluoro-ethylene (PTFE) and values of the complex permittivity of the samples were then computed based on the measured reflection (S₁₁) and transmission (S₂₁) coefficients. Verification of the experimental measurement techniques were done by measuring the values of the complex permittivity of the samples of known dielectric properties such as flexiglass and teflon. Also, TRL calibration technique and time-domain gating feature in vector network analyzer were used to eliminate errors due multiple reflections. It was shown that the values of complex permittivity increases as the percentage of carbon black in rubber composite increases.