Planar Microwave Resonant Sensors: A Review and Recent Developments

Abstract

Microwave sensors based on electrically small planar resonant elements are reviewed in this paper. By virtue of the high sensitivity of such resonators to the properties of their surrounding medium, particularly the dielectric constant and the loss factor, these sensors are of special interest (although not exclusive) for dielectric characterization of solids and liquids, and for the measurement of material composition. Several sensing strategies are presented, with special emphasis on differential-mode sensors. The main advantages and limitations of such techniques are discussed, and several prototype examples are reported, mainly including sensors for measuring the dielectric properties of solids, and sensors based on microfluidics (useful for liquid characterization and liquid composition). The proposed sensors have high potential for application in real scenarios (including industrial processes and characterization of biosamples).

Intrinsic Dielectric Loss in Zr0.8Sn0.2TiO4 Ceramics Investigated by Terahertz Time Domain Spectroscopy

“…These materials were successfully used in passive devices like oscillators, multiplexers, filters, metamaterials, antennas, etc. [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ]. Even though a large number of dielectrics with suitable properties have been reported [ 10 , 11 , 12 , 13 , 14 , 15 ], their mass production is restricted due to the manufacturing costs and technological limitations.…”

Passive Resonant Sensors: Trends and Future Prospects

“…Genarellil et al used a resonant cavity to evaluate NaCl concentration without microfluidic set-up. The interest of this approach is to obtain a direct estimation of the dielectric properties of the complete sample without dissociating the medium and the pollutant [139]. Very recently, Rossignol et al [140] demonstrated an accurate quantification of chemical species at trace levels in a complex liquid with a microwave sensor.…”

Patch antenna sensor for wireless ice and frost detection

“…These advantages have inspired the use of microwave resonators for various sensing applications including ice sensing 21 – 38 . Microwave resonator sensors operate by monitoring the interaction between high concentrations of electric field (E-field) and a material under test, allowing for material property changes to be observed in real time 39 . In ice detection studies utilizing resonator structures, the microwave sensors were able to detect the accumulation of ice, the thickness of the accreted ice, and the rate of deposition on their surface.…”