University of Oulu

Masrakin, K., Ibrahim, S. Z., Rahim, H. A., Azemi, S. N., Soh, P. J., & Tantiviwat, S. (2023). Microstrip Sensor Based on Ring Resonator Coupled with Double Square Split Ring Resonator for Solid Material Permittivity Characterization. Micromachines, 14(4), 790.

Microstrip sensor based on ring resonator coupled with double square split ring resonator for solid material permittivity characterization

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Author: Masrakin, Khuzairi1,2; Ibrahim, Siti Zuraidah1,2; Rahim, Hasliza A.1,2;
Organizations: 1Faculty of Electronic Engineering & Technology, Universiti Malaysia Perlis (UniMAP), Arau 02600, Malaysia
2Advanced Communication Engineering Centre of Excellence (ACE), Universiti Malaysia Perlis (UniMAP), Kangar 01000, Malaysia
3Centre for Wireless Communications (CWC), University of Oulu, 90014 Oulu, Finland
4Faculty of Industrial Education and Technology, Rajamangala University of Technology Srivijaya, Songkhla 90000, Thailand
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 9.7 MB)
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Language: English
Published: Multidisciplinary Digital Publishing Institute, 2023
Publish Date: 2023-09-08


This paper analyzes a microwave resonator sensor based on a square split-ring resonator operating at 5.122 GHz for permittivity characterization of a material under test (MUT). A single-ring square resonator edge (S-SRR) is coupled with several double-split square ring resonators to form the structure (D-SRR). The function of the S-SRR is to generate a resonant at the center frequency, whereas D-SRRs function as sensors, with their resonant frequency being very sensitive to changes in the MUT’s permittivity. In a traditional S-SRR, a gap emerges between the ring and the feed line to improve the Q-factor, but the loss increases as a result of the mismatched coupling of the feed lines. To provide adequate matching, the microstrip feed line is directly connected to the single-ring resonator in this article. The S-SRR’s operation switches from passband to stopband by generating edge coupling with dual D-SRRs located vertically on both sides of the S-SRR. The proposed sensor was designed, fabricated, and tested to effectively identify the dielectric properties of three MUTs (Taconic-TLY5, Rogers 4003C, and FR4) by measuring the microwave sensor’s resonant frequency. When the MUT is applied to the structure, the measured findings indicate a change in resonance frequency. The primary constraint of the sensor is that it can only be modeled for materials with a permittivity ranging from 1.0 to 5.0. The proposed sensors’ acceptable performance was achieved through simulation and measurement in this paper. Although the simulated and measured resonance frequencies have shifted, mathematical models have been developed to minimize the difference and obtain greater accuracy with a sensitivity of 3.27. Hence, resonance sensors offer a mechanism for characterizing the dielectric characteristics of varied permittivity of solid materials.

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Series: Micromachines
ISSN: 2072-666X
ISSN-E: 2072-666X
ISSN-L: 2072-666X
Volume: 14
Issue: 4
Article number: 790
DOI: 10.3390/mi14040790
Type of Publication: A1 Journal article – refereed
Field of Science: 213 Electronic, automation and communications engineering, electronics
Funding: This research was funded by the Ministry of Higher Education (MOHE) and Universiti Malaysia Perlis (UniMAP), grant number FRGS/1/2019/STG02/UNIMAP/02/5. The APC was funded by FRGS/1/2019/STG02/UNIMAP/02/5. In addition, the author would like to acknowledge the financial support in the form of a publication incentive grant from Universiti Malaysia Perlis (UniMAP).
Copyright information: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (