Improved approach using multiple planar complementary split-ring resonators for accurate measurement of permittivity

This paper presents a non-destructive planar single-compound triple complementary split-ring resonator (TCSRR) to improve the measurement of the dielectric constants of a material under test (MUT). This proposed microwave sensor technology requires the multiple-square concentric ring to generate multiple non-identical frequency responses to take estimate for dielectric property measurement, and the cooperated estimate of SC-TCSRR can effectively mitigate the permittivity measurement error. The dielectric constants and thickness of a MUT are dependent on the operational resonance frequency deviation. The CSRR sensor is etched on the ground plane of a microstrip line. The SC-TCSRR sensor operating between 1.5 GHz to 4.6 GHz band is fabricated by specific ratio range and tested for verification. For calculation and analysis, the permittivity of a MUT is extracted by two resonant frequencies (f_M, f_H). This proposed method uses three sets (f_M, f_H), f_L, f_M) and f_L, f_H) and averages the measured results to improve measurement accuracy. The experiments yielded average measurement errors less than 1.60 % for the permittivity of MUT. And, the result is more accurate than dual ring CSRR's measurement error result [1] 4.63%. This effective TCSRR sensor offers low computational costs, easy fabrication and precise measurement.