A Microstrip Coupled Cylindrical Dielectric Resonator as a Displacement Sensor

Abstract

This paper presents the numerical and experimental investigations on the use of a cylindrical dielectric resonator (DR) as a displacement sensor in the millimetre range, for the first time. The sensor principle is based on the sensitivity of the coupling between a resonator and a transmission line, which is a simple microstrip line in the present context, to positional changes (displacement) of the resonator. Corresponding change in the input reflection coefficient of the microstrip line can be used to quantify the displacement. It is demonstrated numerically that the sensitivity and the linearity of the displacement sensing are highly dependent on the dielectric constant of the DR, a feature that is absent in other resonator-based sensors. Experimental results for an available DR sample of dielectric constant 24, diameter 19.43 mm and height 7.3 mm, operating in the HEM_11δ mode with a resonant frequency of 3.41 GHz are presented to validate the simulations. Analysis of the results shows that in the measurement range of 1–8 mm, the above arrangement gives a sensitivity of 2.01 dB/mm. Such displacement sensors may find application in strain or pressure measurement, as well as in diagnosing alignment or positional errors.

KEYWORDS:

• Coupling coefficient
• Dielectric resonator
• Hybrid mode
• Impedance matching
• Microstrip line
• Proximity coupling

Acknowledgments

Authors acknowledge the Department of Science and Technology (DST), Govt. of India for supporting the work through the FIST grant [Ref: SR/FST/ETI-346/2013]. The first author also acknowledges Science and Engineering Research Board (DST-SERB) for providing financial support for the work [File No. EMR/2017/001126].

Additional information

Notes on contributors

A.V. Praveen Kumar

A V Praveen Kumar received his PhD degree in microwave electronics from the Department of Electronics, Cochin University of Science and Technology (CUSAT), Kerala, in 2009. His thesis was on the fabrication, characterization and development of dielectric resonators and its application in wideband dielectric resonator antennas. He joined the Engineering Department, Lancaster University, UK, as a postdoctoral fellow where he worked on the development of radiofrequency cavities for particle accelerators. Presently, he is working as an assistant professor in the Department of Electrical and Electronics Engineering, Birla Institute of Technology and Science, Pilani (BITS Pilani), Rajasthan, India. His major research interest is in RF and microwave engineering which includes antennas, cavity resonators, particle accelerators and material characterization. He has published several international journal/conference papers on various aspects of RF engineering. Corresponding Author. Email: [email protected]

Anuj Kumar Ojha

Anuj Kumar Ojha received his MTech degree in digital communication from Rajasthan Technical University (RTU), Kota Rajasthan in 2013. Later he joined the MEMS group at CSIR-CEERI Pilani, Rajasthan, as the project fellow, where he worked on the development of silicon based MEMS pizoresistive pressure sensors for various applications. He has published journal/conference papers on various aspects of MEMS sensors. Presently, he is pursuing PhD degree at the Department of Electrical and Electronics Engineering, Birla Institute of Technology and Science, Pilani, (BITS Pilani), Rajasthan, India. His research interests include dielectric resonators based physical sensors and dielectric resonator antennas. Email: [email protected]