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Abstract

A new compact tri-band elliptical microstrip resonator is proposed for noninvasive microwave-based glucose sensing using a thumb-contact configuration. The sensor consists of concentric elliptical copper rings with a localized outer-ring slot and capacitive feed coupling, implemented on an FR-4 substrate to enhance electric-field confinement beneath the thumb-loading region. A multilayer cylindrical thumb phantom incorporating dispersive tissue models and glucose-dependent blood permittivity is employed to emulate realistic on-body conditions. Full-wave simulations in the 2-6 GHz band demonstrate three dominant glucose-sensitive resonant modes. Over a concentration range of 0-600 mg/dL, the resonances shift monotonically from 2.054 to 2.142 GHz, 2.83 to 3.214 GHz, and 5.128 to 5.75 GHz, respectively. The corresponding frequency-deviation rates are 0.147, 0.64, and 1.037 MHz/(mg/dL), with the highest linearity reaching R² ≈ 0.98. By distributing sensing across three coupled resonant modes, the proposed approach enables frequency-diverse feature extraction suitable for multivariate calibration, improving robustness against contact variability and modeling uncertainties compared with single-band configurations.

1. World Health Organization, "Diabetes," Fact sheet, Nov. 2024.

2. International Diabetes Federation, "IDF diabetes atlas," Brussels, Belgium, 2025.

3. American Diabetes Association Professional Practice Committee for Diabetes, "7. Diabetes technology: Standards of care in diabetes --- 2026," Diabetes Care, Vol. 49, No. Supplement_1, S150–S165, 2025.
doi:10.2337/dc26-S007 Google Scholar

4. Natale, Patrizia, Sharon Chen, Clara K. Chow, Ngai Wah Cheung, David Martinez-Martin, Corinne Caillaud, Nicole Scholes-Robertson, Ayano Kelly, Jonathan C. Craig, Giovanni Strippoli, and Allison Jaure, "Patient experiences of continuous glucose monitoring and sensor‐augmented insulin pump therapy for diabetes: A systematic review of qualitative studies," Journal of Diabetes, Vol. 15, No. 12, 1048-1069, 2023.
doi:10.1111/1753-0407.13454 Google Scholar

5. Alahnomi, Rammah Ali, Zahriladha Zakaria, Zulkalnain Mohd Yussof, Ayman Abdulhadi Althuwayb, Ammar Alhegazi, Hussein Alsariera, and Norhanani Abd Rahman, "Review of recent microwave planar resonator-based sensors: Techniques of complex permittivity extraction, applications, open challenges and future research directions," Sensors, Vol. 21, No. 7, 2267, 2021.
doi:10.3390/s21072267 Google Scholar

6. Liu, Changjun, Chongwei Liao, Yujie Peng, Weixin Zhang, Bo Wu, and Peixiang Yang, "Microwave sensors and their applications in permittivity measurement," Sensors, Vol. 24, No. 23, 7696, 2024.
doi:10.3390/s24237696 Google Scholar

7. Kiani, Sina, Pejman Rezaei, and Mina Fakhr, "Dual-frequency microwave resonant sensor to detect noninvasive glucose-level changes through the fingertip," IEEE Transactions on Instrumentation and Measurement, Vol. 70, 1-8, 2021.
doi:10.1109/tim.2021.3052011 Google Scholar

8. Mohammadi, Pejman, Ali Mohammadi, and Ali Kara, "Dual-frequency microwave resonator for noninvasive detection of aqueous glucose," IEEE Sensors Journal, Vol. 23, No. 18, 21246-21253, 2023.
doi:10.1109/jsen.2023.3303170 Google Scholar

9. Farouk, Mariam, Anwer S. Abd El-Hameed, Angie R. Eldamak, and Dalia N. Elsheakh, "Noninvasive blood glucose monitoring using a dual band microwave sensor with machine learning," Scientific Reports, Vol. 15, No. 1, 16271, 2025.
doi:10.1038/s41598-025-94367-6 Google Scholar

10. Ong, Woon May, Siew Siang Chua, and Chirk Jenn Ng, "Barriers and facilitators to self-monitoring of blood glucose in people with type 2 diabetes using insulin: A qualitative study," Patient Preference and Adherence, Vol. 8, 237-246, 2014.
doi:10.2147/ppa.s57567 Google Scholar

11. Janapala, Rajesh Naidu, Joseph S. Jayaraj, Nida Fathima, Tooba Kashif, Norina Usman, Amulya Dasari, Nusrat Jahan, and Issac Sachmechi, "Continuous glucose monitoring versus self-monitoring of blood glucose in type 2 diabetes mellitus: A systematic review with meta-analysis," Cureus, Vol. 11, No. 9, e5634, 2019.
doi:10.7759/cureus.5634 Google Scholar

12. Shi, Jiale, Raúl Fernández-García, and Ignacio Gil, "Sensor technologies for non-invasive blood glucose monitoring," Sensors, Vol. 25, No. 12, 3591, 2025.
doi:10.3390/s25123591 Google Scholar

13. Alsultani, Ameer B., Katalin Kovács, J. Geoffrey Chase, and Balazs Benyo, "Advances in invasive and non-invasive glucose monitoring: A review of microwave-based sensors," Sensors and Actuators Reports, Vol. 9, 100332, 2025.
doi:10.1016/j.snr.2025.100332 Google Scholar

14. Singh, Tilakdhari, Piyush Kumar Mishra, Aditya Pal, and Vijay Shanker Tripathi, "A planar microwave sensor for noninvasive detection of glucose concentration using regression analysis," International Journal of Microwave and Wireless Technologies, Vol. 15, No. 8, 1343-1353, 2023.
doi:10.1017/s1759078723000545 Google Scholar

15. Kandwal, Abhishek, Ziheng Ju, Louis W. Y. Liu, Rohit Jasrotia, Choon Kit Chan, Zedong Nie, Ali M. Almuhlafi, and Hamsakutty Vettikalladi, "A dual-band microwave sensor for glucose measurements utilizing an enclosed split ring metamaterial-based array," Engineering Science and Technology, an International Journal, Vol. 62, 101947, 2025.
doi:10.1016/j.jestch.2025.101947 Google Scholar

16. Mansour, Esraa, Mohamed I. Ahmed, Ahmed Allam, Ramesh K. Pokharel, and Adel B. Abdel-Rahman, "Sensitivity evaluation of a dual-finger metamaterial biosensor for non-invasive glycemia tracking on multiple substrates," Sensors, Vol. 25, No. 22, 7034, 2025.
doi:10.3390/s25227034 Google Scholar

17. Krishnan, Rahul, Vanaja Selvaraj, Nagarajan Pandian, Sheela Sammandhan, Inam Ullah Khan, and Sai Kiran Oruganti, "A compact dielectric resonator antenna based microwave sensor for non-invasive blood glucose monitoring," Instrumentation, Mesure, Metrologie, Vol. 24, No. 5, 297-304, 2025.
doi:10.18280/i2m.240501 Google Scholar

18. Soltanian, Farzad, Mehdi Nosrati, Saleh Mobayen, Chuan-Chun Li, Telung Pan, Ming-Ta Ke, and Paweł Skruch, "On-body non-invasive glucose monitoring sensor based on high figure of merit (FoM) surface plasmonic microwave resonator," Scientific Reports, Vol. 13, No. 1, 17527, 2023.
doi:10.1038/s41598-023-44435-6 Google Scholar

19. Krishna, Raghupatruni Ram, "A 3.1 GHz defected ground transmission line microwave sensor for blood glucose estimation," Progress In Electromagnetics Research Letters, Vol. 123, 83-88, 2025.
doi:10.2528/pierl24090302 Google Scholar

20. Zaarour, Youness, Fatimazahrae El Arroud, Tomas Fernandez, Juan Luis Cano, Rafiq El Alami, Otman El Mrabet, Abdelouheb Benani, Abdessamad Faik, and Hafid Griguer, "Microwave antenna sensing for glucose monitoring in a vein model mimicking human physiology," Biosensors, Vol. 15, No. 5, 282, 2025.
doi:10.3390/bios15050282 Google Scholar

Dr. Amjad Hussein Yousif

Dr. Saad Wasmi Osman Luhaib

Dr. Mohammed Younis Thanoun