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Sensors 2016, 16(10), 1556;

Six-Port Based Interferometry for Precise Radar and Sensing Applications

Institute for Electronics Engineering, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen D-91058, Germany
Author to whom correspondence should be addressed.
Academic Editors: Changzhi Li, Roberto Gómez-García and José-María Muñoz-Ferreras
Received: 14 June 2016 / Revised: 2 September 2016 / Accepted: 13 September 2016 / Published: 22 September 2016
(This article belongs to the Special Issue Non-Contact Sensing)
PDF [2636 KB, uploaded 22 September 2016]


Microwave technology plays a more important role in modern industrial sensing applications. Pushed by the significant progress in monolithic microwave integrated circuit technology over the past decades, complex sensing systems operating in the microwave and even millimeter-wave range are available for reasonable costs combined with exquisite performance. In the context of industrial sensing, this stimulates new approaches for metrology based on microwave technology. An old measurement principle nearly forgotten over the years has recently gained more and more attention in both academia and industry: the six-port interferometer. This paper reviews the basic concept, investigates promising applications in remote, as well as contact-based sensing and compares the system with state-of-the-art metrology. The significant advantages will be discussed just as the limitations of the six-port architecture. Particular attention will be paid to impairment effects and non-ideal behavior, as well as compensation and linearization concepts. It will be shown that in application fields, like remote distance sensing, precise alignment measurements, as well as interferometrically-evaluated mechanical strain analysis, the six-port architecture delivers extraordinary measurement results combined with high measurement data update rates for reasonable system costs. This makes the six-port architecture a promising candidate for industrial metrology. View Full-Text
Keywords: six-port; interferometer; radar; industrial sensing; microwave sensor six-port; interferometer; radar; industrial sensing; microwave sensor

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Koelpin, A.; Lurz, F.; Linz, S.; Mann, S.; Will, C.; Lindner, S. Six-Port Based Interferometry for Precise Radar and Sensing Applications. Sensors 2016, 16, 1556.

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