Simplified three-strip coupled-line section as microwave sensor for dielectric materials measurement

This paper presents novel microwave sensor constructed of simplified three-strip coupled-line section featuring increased sensitivity allowing for measurement of small dielectric material samples for industrial and medical applications. To characterize the sample which at least must be of size of the distance between coupled-strips, a differential excitation is provided to the sensor since the sample significantly more affects the mutual capacitance existing between sensors' coupled strips than the self-capacitance, which is created between the strips and the ground area. The proposed sensor has been theoretically and experimentally investigated and obtained performance has been compared to performance of recently developed two-strip coupled-line sensor. The obtained results proved the correctness and usability of the proposed circuit.