A Simplified RF Technique to Estimate the Conductivity of Metal Composites

In this work, an innovative and simplified RF (radio frequency) approach is presented to determine the conductivity of the test specimen at RF regime. A modified split pi (MSPi) shaped design topology coupled to a microstrip line is utilized as the conductivity sensor topology. The designed structure requires the placement of test specimen to convert the overall shape of the sensing element into an asymmetric rectangular split ring resonator (ARSSR). It produces a substantial notch level at the corresponding resonant frequency. The notch level of the ARSSR changes with the change in the RF conductive loss associated with the conductive test specimen. The sizes of different arms including test specimen parameters are optimized accordingly to attain a wide linear range with good conductivity resolution. The performance of the sensor is numerically verified corresponding to the conductivity range of standard metal sample (1e7 S/m), metallic composites and conductive inks (1e4 S/m). Simulation studies show that the sensor can determine the conductivity of samples with the conductivity range from 1e7 S/m to 1e4 S/m. The MSPi structure prototype is fabricated and tested with copper and aluminum samples. The measured results are in line with the idea proposed in this paper.