Abstract
This study focuses on the microwave characterisation of a microstrip resonator aimed for gas sensing applications. The developed one-port microstrip resonator, consisting of three concentric rings with a central disk, is coupled to a 50-Ohm microstrip feedline through a small gap. A humidity sensing layer is deposited on this gap by drop-coating an aqueous solution of Ag@alpha-Fe<sub>2</sub>O<sub>3</sub> nanocomposite. The operation principle of the developed humidity sensor is based on the change of the dielectric properties of the Ag@alpha-Fe<sub>2</sub>O<sub>3</sub> nanocomposite when the relative humidity is varied. However, it should be underlined that, depending on the choice of the sensing material, different target gases of interest can be detected with the proposed structure. The frequency-dependent response of the sensor is obtained using the reflection coefficient measured from 3.5 GHz to 5.6 GHz with relative humidity ranging from 0 %rh to 83 %rh. The variation of the humidity concentration strongly impacts on the two resonances detected in the measured reflection coefficient. In particular, an increase of the humidity level leads to lowering both resonant frequencies, which can be used as sensing parameters for humidity monitoring purpose. An exponential function has been used to accurately model the two resonant frequencies as a function of the humidity.
Highlights
Nowadays, the research interests in the development of sensors with extremely low-power consumption is growing because of the increasingly energy-saving requirements of the expanding market
Following on from the results of our previous study [28], we present here a thorough investigation of a one-port gas transducer based on a microwave microstrip resonator, which is validated as humidity sensor by using an Ag@α-Fe2O3 nanocomposite as a sensing material
A one-port microwave gas transducer was developed by coupling a microstrip resonator for electromagnetic wave propagation with an Ag@α-Fe2O3 nanocomposite for humidity
Summary
The research interests in the development of sensors with extremely low-power consumption is growing because of the increasingly energy-saving requirements of the expanding market. The planar microstrip technology is widely employed in the fabrication of microwave components like antennas, filters, and resonators Such devices are often used in sensing applications because of their low cost, easy fabrication, and good performance [20]-[24]. Following on from the results of our previous study [28], we present here a thorough investigation of a one-port gas transducer based on a microwave microstrip resonator, which is validated as humidity sensor by using an Ag@α-Fe2O3 nanocomposite as a sensing material. The resonant frequencies (fR1 and fR2) associated to the two dips observed in can be directly used as humidity sensing parameters To this end, a sensitivity-based investigation is developed in order to assess the sensing performance of the proposed microwave sensor for humidity monitoring application.
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