Metallized-Substrate Multiband-Permittivity Measurement with NGD Ring Resonator

This paper explores an original research work on multiband metallized-permittivity measurement method for copper-clad substrates based on bandpass (BP) negative group delay (NGD) ring circuit. The multiband permittivity extraction formula from NGD center frequency harmonics is established from S-parameter model. The BP-NGD function specifications of are defined. The BP-NGD ring resonator (RR) proof-of-concept (PoC) consists of linearly coupled loops implemented in microstrip technology. The multiband permittivity measurement NGD-method validity is proved by well-agreed full wave simulations and measurements of NGD RR prototype. The test results of dielectric sample are validated in 1-10 GHz. Furthermore, uncertainty analyses under the maximum processing error are performed. The NGD-method effectiveness is confirmed with permittivity low measurement relative error lower than 0.5%.