Circuit Analysis of a Coplanar Waveguide (CPW) Terminated With a Step-Impedance Resonator (SIR) for Highly Sensitive One-Port Permittivity Sensing
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)
Gil Barba, Marta (Universidad Politécnica de Madrid. Departamento de Ingeniería Audiovisual y Comunicaciones)
Ebrahimi, Amir (Royal Melbourne Institute of Technology. School of Engineering)
Martín, Ferran (Universitat Autònoma de Barcelona. Departament d'Enginyeria Electrònica)

Date:	2022
Abstract:	This paper presents a single-frequency reflective-mode phase-variation microwave sensor devoted to the dielectric characterization of materials. The device is implemented in coplanar waveguide (CPW) technology and consists of two parts: (i) the sensing region, a step-impedance resonator (SIR) as termination of a CPW transmission line, and (ii) the design region, a cascade of high/low impedance quarter-wavelength inverters, used to boost up the sensitivity. By placing the so-called material under test (MUT) on top of the sensing region, the capacitance of the SIR is altered due to the effects of the dielectric constant of the MUT. This modifies the phase of the reflection coefficient seen from the input port, the output variable. From a circuit analysis, it is demonstrated that the sensitivity for small perturbations in the vicinity of the dielectric constant of a reference (REF) material can be optimized by setting the operation frequency of the sensor to the resonance frequency of the SIR loaded with such REF material. The maximum sensitivity in one of the reported sensors is as high as 66. 5°, and the main figure of merit, defined as the ratio between the maximum sensitivity and the area of the sensing region expressed in terms of the squared guided wavelength, is FoM=3643∘/λ2 . Such figure of merit represents a significant improvement as compared to the one of the equivalent sensor implemented by means of an open-ended quarter-wavelength sensing line. Such equivalence between the semi-lumped element (i. e. , SIR-based) sensor and the fully distributed counterpart is also analyzed in the paper.
Grants:	Agencia Estatal de Investigación PID2019-103904RB-I00 Agencia Estatal de Investigación PDC2021-121085-I00 Agència de Gestió d'Ajuts Universitaris i de Recerca 2017/SGR-1159 Agencia Estatal de Investigación FPU20/05700 Ministerio de Ciencia e Innovación IJC2019-040786-I
Note:	Altres ajuts: Secreteraria d'Universitats i Recerca (Generalitat de Catatunya), European Social Fund for the FI Grant, Institució Catalana de Recerca i Estudis Avançats
Rights:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original.
Language:	Anglès
Document:	Article ; recerca ; Versió publicada
Subject:	Coplanar waveguide (CPW) ; Dielectric characterization ; Microwave sensor ; Phase-variation sensor ; Permittivity sensor ; Reflective-mode sensor ; Step-impedance resonator (SIR)
Published in:	IEEE Access, Vol. 10 (June 2022) , p. 62597-62612, ISSN 2169-3536

DOI: 10.1109/ACCESS.2022.3181195

16 p, 1.9 MB

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