On the Sensitivity of Reflective-Mode Phase-Variation Sensors Based on Open-Ended Stepped-Impedance Transmission Lines: Theoretical Analysis and Experimental Validation
Muñoz Enano, Jonathan (Universitat Autònoma de Barcelona. Departament d'Enginyeria Electrònica)
Vélez Rasero, Paris (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)
Casacuberta Orta, Pau (Universitat Autònoma de Barcelona. Departament d'Enginyeria Electrònica)
Martín, Ferran (Martín Antolín) (Universitat Autònoma de Barcelona. Departament d'Enginyeria Electrònica)

Date:	2021
Abstract:	This article presents an exhaustive study of the sensitivity in reflective-mode phase-variation sensors based on an open-ended transmission line with a step-impedance discontinuity. Such discontinuity delimits the sensing region (which extends up to the open end of the so-called sensing line), from the transmission line section connected to the input port (design line), which is used to enhance the sensitivity. The theoretical analysis provides the design guidelines to achieve a sensor with high sensitivity compared with the one based on an ordinary (uniform) line with a similar length. In particular, it is shown that for sensitivity optimization, the electrical length of the design line must be set to 90° (or an odd multiple), whereas either a 90° (or an odd multiple) or a 180° (or an even or odd multiple) sensing line can be alternatively used in order to maximize the sensitivity. It is shown that the impedance contrast, defined as the ratio between the characteristic impedances of the design and sensing line, is a key parameter for sensitivity enhancement, and it must be as low or as high as possible for the 90° or 180° sensing lines, respectively. For validation purposes, two prototype devices (one with a 90° and the other one with a 180° sensing line) have been designed and fabricated following the design guidelines. Such devices have been tested by loading the sensing region with several materials with different dielectric constants. Compared with the ordinary line-based sensors, it is found that the maximum sensitivity is enhanced by a factor of 19. 7 and 11. 4 in the phase-variation sensor based on a 90° and 180° sensing line, respectively. Finally, the sensor concept is generalized to a multisection step-impedance transmission line as a means of further increasing the sensitivity, and a prototype device exhibiting 528. 7° maximum sensitivity is implemented.
Grants:	Ministerio de Ciencia e Innovación TEC2016-75650-R Agència de Gestió d'Ajuts Universitaris i de Recerca 2017/SGR-1159 Ministerio de Ciencia e Innovación IJCI-2017-31339
Note:	Altres ajuts: Universidad Politécnica de Madrid Young Researchers (Grant Number: VJIDOCUPM18MGB) i ICREA
Rights:	Tots els drets reservats.
Language:	Anglès
Document:	Article ; recerca ; Versió acceptada per publicar
Subject:	Microstrip ; Microwave sensor ; Phase-variation sensor ; Reflective-mode sensor ; Stepped-impedance transmission line
Published in:	IEEE transactions on microwave theory and techniques, Vol. 69, Issue 1 (January 2021) , p. 308-324, ISSN 0018-9480

DOI: 10.1109/TMTT.2020.3023728

Postprint 16 p, 1.3 MB

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