Highly Sensitive Open-Ended Coaxial Cable-Based Microwave Resonator for Humidity Sensing


A novel portable open-ended hollow coaxial cable resonator (OE-HCCR) is proposed and demonstrated for direct relative humidity (RH) measurements without the assistance of any humidity-sensitive material. The sensor is fabricated from a homemade hollow coaxial cable platform that provides ease of modification and improved robustness. The microwave cavity resonator is a metal post-coupled open-ended coaxial resonator, which includes two highly-reflective reflectors, i.e., the metal post and the metal plate-backed open end of the coaxial line. The gap distance between the metal plate and the open end is defined by a circular spacer. By simple one-step adjustments of the thickness of the spacer, the RH measurement sensitivity of the OE-HCCR can be greatly enhanced. The device physics is discussed; numerical calculations and experimental investigations are conducted to verify the sensitivity enhancement of the OE-HCCR for RH sensing. Due to the increased sensitivity, this is the first report of an open-ended coaxial line that is able to directly sense gaseous analyte, to the best of our knowledge. The proposed OE-HCCR with the sensitivity enhancement has the potential for highly sensitive chemical sensing combined with functional materials.


Electrical and Computer Engineering


National Science Foundation, Grant 2027571

Keywords and Phrases

Enhanced Sensitivity; Humidity Sensing; Microwave Device; Microwave Resonator; Open-Ended Coaxial Cable Resonator

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Document Type

Article - Journal

Document Version


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© 2020 Elsevier, All rights reserved.

Publication Date

03 Aug 2020