Far-Field Microcontroller Based Automated Microwave Measurement System for Characterization of Dielectric Permittivity of High-Loss Materials

A microcontroller based microwave free-space measurement system for a real-time determination of dielectric permittivity of high loss planar materials is proposed. The measurement system is comprised of two main sections - microwave and electronic sections. While microwave section of the system provides for measuring only amplitudes of transmission and reflection coefficients using free-space method at one fixed frequency, the electronic section of the system processes these data and provides output result by using a microcontroller. Measurements of reflection and transmission properties of mortar and cement paste samples with different water-to-cement (w/c) ratios at 8.5 GHz are conducted for validation of the proposed system, and complex permittivity of 1-day aged mortar samples with different w/c ratios is computed. It is shown that computed permittivities are in good agreement with previous studies. The simplicity, applicability, and relatively inexpensive structure of the proposed measurement system with its present state may still be useful for some applications