In this study, a double reentrant cavity sensor (DRECS) loaded with ring gaps is proposed to characterize the displacement that the metal plate is inserted into the DRECS. The conventional substrate-parasitic-capacitance of DRECS in the substrate integrated waveguide (SIW) configuration, which has no contribution to the sensitivity, is successfully eliminated by using a symmetric double reentrant cavity. The ring gaps are introduced in SIW DRECS to effectively suppress the fringe electric field around the post, and enlarge the range of displacement measurements. Additionally, a displacement model, which is characterized by the quantitative relationship between the resonant frequency of DRECS and insertion depth inside DRECS, is theoretically established with the help of the electric field distribution and the equivalent circuit of the DRECS. A prototype of the designed sensor is fabricated and measured. The sensor work at 1.5-3.1 GHz and the measured results are in good agreement with the simulated ones from the displacement model. The measurement results indicate that the sensor has a displacement test range of 27 mm and Q-factor of over 150, and can achieve high sensitivity of 58 MHz/mm.
2. Huang, J., J. Li, G. Xu, and Z. Wei, "A microfluidic sensor based on meta-surface absorber for rapidand nondestructive identification of edible oil species," Progress In Electromagnetics Research C, Vol. 96, 153-163, 2019.
3. Al-Duhni, G. and N. Wongkasem, "Metal discovery by highly sensitive microwave multi-band metamaterial-inspired sensors," Progress In Electromagnetics Research B, Vol. 93, 1-22, 2021.
4. Bait-Suwailam, M. M., "Numerical assessment of red palm weevil detection mechanism in palm trees using CSRR microwave sensors," Progress In Electromagnetics Research Letters, Vol. 100, 63-71, 2021.
5. Teng, C., C. H. Chio, K. W. Tam, and P. Y. Lau, "An angular displacement microwave sensor with 360◦ dynamic range using multi-mode resonator," IEEE Sensors Journal, Vol. 21, No. 3, 2899-2907, February 1, 2021.
6. Naqui, J., M. Durán-Sindreu, and F. Martín, "Novel sensors based the symmetry properties of Split Ring Resonators (SRRs)," Sensors, Vol. 11, 7545-7553, 2011.
7. Naqui, J., M. Durán-Sindreu, and F. Martín, "Alignment and position sensors based on split ring resonators," Sensors, Vol. 12, 11790-11797, 2012.
8. Rezaee, M. and M. Joodaki, "Two-dimensional displacement sensor based on CPW line loaded by Defected Ground Structure (DGS) with two separated transmission zeroes," IEEE Sensors Journal, Vol. 17, No. 4, 994-999, February 15, 2017.
9. Saadat-Safa, M., V. Nayyeri, M. Khanjarian, M. Soleimani, and O. M. Ramahi, "A CSRR-based sensor for full characterization of magneto-dielectric materials," IEEE Transactions on Microwave Theory and Techniques, Vol. 67, No. 2, 806-814, February 2019.
10. Soltan, A., R. A. Sadeghzadeh, and S. Mohammad-Ali-Nezhad, "Angular displacement sensor based on Corrugated Substrate Integrated Waveguide (CSIW)," IETE Journal of Research, August 13, 2020.
11. Horestani, A. K., et al., "Displacement sensor based on diamond-shaped tapered split ring resonator," IEEE Sensors Journal, Vol. 13, No. 4, 1153-1159, April 2013.
12. Salim, A., S.-H. Kim, J. Y. Park, and S. Lim, "Microfluidic biosensor based on microwave substrate-integrated waveguide cavity resonator," Journal of Sensors, 1-13, 2018.
13. Chen, C.-M., J. Xua, and Y. Yao, "Fabrication of miniaturized CSRR-loaded HMSIW humidity sensors with high sensitivity and ultra-low humidity hysteresis," Sensors and Actuators B: Chemical, 1100-1106, 2018.
14. Soltan, A., R. A. Sadeghzadeh, and S. Mohammad-Ali-Nezhad, "High sensitivity simple structured displacement sensor using Corrugated Substrate-Integrated Waveguide (CSIW)," IET Microwaves, Antennas & Propagation, Vol. 14, 414-418, 2020.
15. Xi, W., W. R. Tinga, W. A. Geoffrey Voss, and B. Q. Tian, "New results for coaxial re-entrant cavity with partially dielectric filled gap," IEEE Transactions on Microwave Theory and Techniques, Vol. 40, No. 4, 747-753, 1992.
16. Murugkar, A., R. Panigrahi, and K. J. Vinoy, "A novel approach for high Q microwave re-entrant cavity resonator at S-band," Proceedings of the Asia-Pacific Microwave Conference, 1-4, December 2016.
17. Asua, E., V. Etxebarria, and J. Feutchwanger, "High-precision displacement sensor based on resonant cavities through an electronic interface based on Arduino," Sensors and Actuators A: Physical, 296-301, 2019.
18. Saeedi, S., J. Lee, H. H. Sigmarsson, and , "Tunable, high-Q, substrate-integrated, evanescent- mode cavity bandpass-bandstop filter cascade," IEEE Microwave and Wireless Components Letters, Vol. 26, No. 4, 240-242, April 2016.
19. Chen, Y., J. Huang, Y. Xiang, L. Fu, W. Gu, and Y. Wu, "A modified SIW re-entrant microfluidic microwave sensor for characterizing complex permittivity of liquids," IEEE Sensors Journal, Vol. 21, No. 13, 14838-14846, July 1, 2021.
20. Wei, Z., J. Huang, J. Li, G. Xu, Z. Ju, X. Liu, and X. Ni, "A high-sensitivity microfluidic sensor based on a substrate integrated waveguide re-entrant cavity for complex permittivity measurement of liquids," Sensors, Vol. 18, 4005, 2018.
21. Bansiwal, A., S. Raina, K. J. Vinoy, and S. K. Datta, "Calculation of equivalent circuit parameters of a rectangular reentrant cavity for klystron," International Journal of Microwave and Optical Technology, Vol. 13, No. 6, 487-492, November 2018.
22. Abdelfattah, M., D. Peroulis, and , "High-Q tunable evanescent-mode cavity SIW resonators and filters with contactless tuners," IEEE Transactions on Microwave Theory and Techniques, Vol. 67, No. 9, 3661-3672, September 2019.
23. Pozar, D. M., Microwave Engineering, 3rd Ed., Wiley, Hoboken, NJ, USA, 2005.
24. Varshney, P. K. and M. Jaleel Akhtar, "Permittivity estimation of dielectric substrate materials via enhanced SIW sensor," IEEE Sensors Journal, Vol. 21, No. 10, 12104-12112, May 15, 2021.
25. Zarifi, M. H. and M. Daneshmand, "Monitoring solid particle deposition in lossy medium using planar resonator sensor," IEEE Sensors Journal, Vol. 17, No. 23, 7981-7988, December 1, 2017.
26. Abdolrazzaghi, M. and M. Daneshmand, "Multifunctional ultrahigh sensitive microwave planar sensor to monitor mechanical motion: Rotation, displacement, and stretch," Sensors, Vol. 20, 1184, 2020.