Design of a two-layer concentric ring interdigital capacitor (CRIDC) chipless RFID for soil moisture monitoring

Name: Suwan Janin

Organization : Rajamangala University of Technology Lanna. College of Integrated Science and Technology, Mechatronics Engineering Program

Email : suwanj@rmutl.ac.th

Name: Akkarat Boonpoonga

Organization : King Mongkut’s University of Technology North Bangkok. Faculty of Engineering, Department of Electrical and Computer Engineering

Email : akkarat.b@eng.kmutnb.ac.th

LCSH: Radio frequency identification systems

LCSH: Soil moisture -- Measurement

LCSH: Inventory control

LCSH: Precision farming

Abstract: This paper presents a two-layer concentric ring interdigital capacitor (CRIDC) sensor designed to mitigate the severe signal attenuation typically observed in conventional passive soil moisture monitoring. The proposed structure was evaluated alongside a traditional 7-finger interdigital capacitor (IDC) resonator using CST microwave studio. During electromagnetic simulations, both sensing tags were embedded at a practical 10-cm depth within a dispersive soil model. By eliminating sharp 90-degree corners, the CRIDC geometry significantly reduces localized electric field concentrations and galvanic leakage. Consequently, while the conventional IDC completely loses its radar cross-section (RCS) resonant signature as soon as volumetric water content (VWC) exceeds 0 percent, the CRIDC maintains a distinct profile in waterlogged conditions up to 50 percent VWC. Simulation results demonstrate that the proposed sensor successfully tracks moisture variations, exhibiting a continuous resonant frequency shift from 1.132 GHz (at 0 percent VWC) down to 0.448 GHz (at 50 percent VWC). This yields a broad dynamic range with a high average sensitivity of 13.68 MHz per percent VWC. These comparative quantitative findings highlight the superior sensitivity and resilience of the continuous ring structure, making the CRIDC an excellent chipless RFID candidate for deep-soil moisture monitoring in precision agriculture.

King Mongkut's University of Technology North Bangkok. Central Library

Address: BANGKOK

Email: library@kmutnb.ac.th

Created: 2026

Modified: 2026-08-17

Issued: 2026-08-17

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BibliograpyCitation : In ECTI Association and Burapha University. Faculty of Engineering. 2026 23rd International Conference on Electrical Engineering/Electronics, Computer, Telecommunications and Information Technology (ECTI-CON 2026) (pp.966-969). Piscataway, NJ : IEEE

eng

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