Parallel-strip line stub resonator for permittivity characterization

Abstract

A new type of a microwave permittivity sensor with a short open stub as a resonator is introduced. The open stub is realized as a double-sided parallel-strip line without a substrate and can be totally immersed into the measured material. It provides high sensitivity of the resonant frequency nearly proportional to the ratio of square roots of dielectric constants of the measured materials. The sensor is tested in two different frequency ranges and for two different dielectric constant ranges (oils and ethanol-water mixture). Its technology is without any additional technological processes such as vias, air-bridges or defected ground structures. Presented sensor is designed, fabricated and tested showing good agreement between simulations and measurements.