A compact planar cylindrical resonant RF sensor for the characterization of dielectric samples

ABSTRACT

A conventional cavity-based planar cylindrical resonant sensor for the RF characterization of dielectric materials is proposed in this work. The designed planar cylindrical sensor is about 22% more compact providing 25% higher sensitivity as compared to its rectangular counterpart working at the same frequency. The proposed sensor is designed for the fundamental TM₀₁₀ mode at 1.5 GHz resonant frequency and is excited using the coaxial probe instead of conventional microstrip feeding, which aids in obtaining further compactness. The sensor is designed on low-cost FR4 substrate and experimentally validated using various dielectric samples like Teflon, polyethylene, PVC and plexiglass yielding a good match between the retrieved dielectric constants and data available in the literature. For characterization of dielectrics, a slot is drilled at the center of the sensor having the maximum electric field for inserting the test sample and later optimized for higher sensitivity. For determining the loss tangent in terms of the transmission coefficient at the resonant frequency, a numerical model is derived using the curve fitting technique.

KEYWORDS:

• Characterization
• cylindrical resonator
• dielectric constant
• microwave sensor
• permittivity measurement
• perturbation method
• planar

ORCID

Prashant Kumar Varshney http://orcid.org/0000-0002-4078-4570

Additional information

Notes on contributors

Prashant Kumar Varshney

Prashant Kumar Varshney is currently pursuing a Ph.D. degree in electrical engineering with the Indian Institute of Technology, Kanpur, India. His current research interest includes designing microwave planar sensors including SIW based resonant sensors and metamaterial inspired resonant sensors for the electromagnetic characterization of materials and imaging of concealed objects. He served as the Vice-chair of the IEEE MTT-S student branch chapter at IIT Kanpur in 2018. He is currently the Chair of IEEE MTT-S student branch chapter at IIT Kanpur.

M. Jaleel Akhtar

M. Jaleel Akhtar is currently working as a full Professor in the Department of Electrical Engineering, IIT Kanpur, India. He has authored two books, two book chapters, and has authored or co-authored over 200 papers in various peer-reviewed international journals and conference proceedings. His current research interests include RF, microwave and THz imaging, microwave non- destructive testing, metamaterial-inspired RF sensors, SIW-based RF devices and sensors, RF energy harvesting, plasmonic devices, functional materials, wideband electromagnetic absorbers. Dr. Akhtar is a fellow of the Institution of Electronics and Telecommunication Engineers, New Delhi, India, and a Life Member of the Indian Physics Association and the Indo-French Technical Association. He served as a Chair of the IEEE Microwave Theory and Techniques Society, Uttar Pradesh Chapter, from 2013 to 2015, and the Vice-Chair of the IEEE, Uttar Pradesh Section, in 2015.