Transmission-Mode Phase-Variation Planar Microwave Sensor Based on a Step-Impedance Shunt Stub for High Sensitivity Defect Detection, Dielectric Constant, and Proximity Measurements
Canalias, Xavier (Universitat Autònoma de Barcelona. Departament d'Enginyeria Electrònica)
Vélez Rasero, Paris (Universitat Autònoma de Barcelona. Departament d'Enginyeria Electrònica)
Casacuberta Orta, Pau (Universitat Autònoma de Barcelona. Departament d'Enginyeria Electrònica)
Su, Lijuan (Universitat Autònoma de Barcelona. Departament d'Enginyeria Electrònica)
Martín, Ferran (Universitat Autònoma de Barcelona. Departament d'Enginyeria Electrònica)

Date:	2025
Abstract:	This article proposes a highly sensitive planar microwave sensor able to detect tiny changes in the dielectric constant of the medium surrounding the sensing element or other variables related to it. The sensor is a two-port structure consisting of a step-impedance shunt stub made of a cascade of high/low-admittance inverters (implemented by means of quarter-wavelength transmission line sections) terminated with an open-ended quarter- or half-wavelength resonator (the sensitive element). The sensor operates in transmission, is fed by a harmonic (single-frequency) signal, and uses the phase of the transmission coefficient at the frequency of the feeding signal as the output variable. The achieved sensitivity in the fabricated prototype, in the limit of small perturbations, is Smax = -227. 9∘ per unit of dielectric constant variation, and the figure of merit (FoM), defined as the ratio between the maximum sensitivity and the area of the sensing region expressed in guided squared wavelengths, is FoM = 7912°/ λ2 . The sensor is the transmission-mode counterpart of previously reported phase-variation sensors based on one-port reflective-mode structures made of a cascade of inverters terminated with a sensing resonator. The advantage of the proposed sensor over those reflective-mode sensors is the fact that the feeding (input) harmonic signal and the (output) signal containing the relevant (phase) information are present at different ports. This fact eases the measurements in applications where, rather than a vector network analyzer (VNA), a phase detector must be used.
Grants:	Agencia Estatal de Investigación PID2022-139181OB-I00 Agència de Gestió d'Ajuts Universitaris i de Recerca 2021/SGR-00192 Ministerio de Ciencia, Innovación y Universidades FPU20/05700 Agencia Estatal de Investigación RYC2022-035819-I Agencia Estatal de Investigación IJC2019-040786-I Agencia Estatal de Investigación PREP2022-000364
Rights:	Aquest material està protegit per drets d'autor i/o drets afins. Podeu utilitzar aquest material en funció del que permet la legislació de drets d'autor i drets afins d'aplicació al vostre cas. Per a d'altres usos heu d'obtenir permís del(s) titular(s) de drets.
Language:	Anglès
Document:	Article ; recerca ; Versió acceptada per publicar
Subject:	Impedance inverter ; Microstrip technology ; Microwave sensor ; Permittivity sensor ; Phase-variation sensor
Published in:	IEEE Transactions on Microwave Theory and Techniques, Vol. 73, Issue 2 (February 2025) , p. 1017-1028, ISSN 0018-9480

DOI: 10.1109/TMTT.2024.3429536

Available from: 2027-02-28 Postprint

The record appears in these collections:
Research literature > UAB research groups literature > Research Centres and Groups (research output) > Engineering > CIMITEC-UAB
Articles > Research articles
Articles > Published articles