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Journal of Sensors
Volume 2015, Article ID 741853, 10 pages
Review Article

Microwave Sensors Based on Symmetry Properties of Resonator-Loaded Transmission Lines

GEMMA/CIMITEC, Departament d’Enginyeria Electrònica, Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, Spain

Received 4 November 2014; Accepted 15 January 2015

Academic Editor: Yanbiao Liao

Copyright © 2015 Jordi Naqui and Ferran Martín. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


This review paper is focused on the design of microwave sensors using symmetry properties of transmission lines loaded with symmetric resonators. The operating principle of these sensors is presented and then several prototype devices are reported, including linear and angular displacement sensors and rotation speed sensors. The main advantage of the proposed sensors is the robustness against changing environmental conditions.