Highly Sensitive Coplanar Waveguide (CPW) reflective-mode phase-variation permittivity sensors based on weakly coupled Step-Impedance Resonators (SIRs)
Casacuberta Orta, Pau (Universitat Autònoma de Barcelona. Departament d'Enginyeria Electrònica)
Vélez Rasero, Paris (Universitat Autònoma de Barcelona. Departament d'Enginyeria Electrònica)
Muñoz Enano, Jonathan (Universitat Autònoma de Barcelona. Departament d'Enginyeria Electrònica)
Su, Lijuan (Universitat Autònoma de Barcelona. Departament d'Enginyeria Electrònica)
Martín, Ferran (Martín Antolín) (Universitat Autònoma de Barcelona. Departament d'Enginyeria Electrònica)

Date:	2024
Abstract:	This article presents a small-sized and highly sensitive planar microwave permittivity sensor based on a pair of weakly coupled step-impedance resonators (SIRs), the sensing elements. The sensor, a one-port structure, is implemented in coplanar waveguide (CPW) technology, and it operates in the reflection mode. The sensing principle is the variation in the phase of the reflection coefficient at the operating frequency, the output variable, caused by the changes in the dielectric constant of the material under test (MUT). This article demonstrates that the maximum sensitivity is inversely proportional to the square of the electric coupling coefficient between the sensing SIRs. Thus, the sensitivity can be unprecedentedly enhanced by merely separating enough the coupled SIRs (thereby reducing their mutual coupling). Since the sensing area is circumscribed to the region occupied by the square (capacitive) patches of the SIRs, it follows that the proposed sensor exhibits also a very high figure of merit ( FoM=26551∘/λ2 ), or ratio between the maximum sensitivity and the size of the sensing area expressed in terms of the squared guided wavelength, λ2.
Grants:	Agencia Estatal de Investigación PID2022-139181OB-I00 Agencia Estatal de Investigación PDC2021-121085-I00 Agencia Estatal de Investigación PID2019-103904RB-I00 Agencia Estatal de Investigación IJC2019-040786-I Agencia Estatal de Investigación FPU20/05700 Agència de Gestió d'Ajuts Universitaris i de Recerca 2021/SGR-00192
Rights:	Tots els drets reservats.
Language:	Anglès
Document:	Article ; recerca ; Versió acceptada per publicar
Subject:	Coplanar waveguide (CPW) ; Coupled resonators ; Microwave sensor ; Permittivity sensor ; Reflective-mode sensor ; Step-impedance resonator (SIR)
Published in:	IEEE transactions on microwave theory and techniques, Vol. 72, no. 3 (March 2024) , p. 1739-1753, ISSN 0018-9480

DOI: 10.1109/TMTT.2023.3308200

Available from: 2026-03-30 Postprint

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Research literature > UAB research groups literature > Research Centres and Groups (research output) > Engineering > CIMITEC-UAB
Articles > Research articles
Articles > Published articles