Multifrequency Coupled-Resonator Sensor for Dielectric Characterization of Liquids

• Published in: IEEE transactions on instrumentation and measurement Vol. 70; pp. 1 - 7
• Main Authors: Herrera Sepulveda, Lyda Vanessa, Olvera Cervantes, Jose Luis, Saavedra, Carlos E.
• Format: Journal Article
• Language: English
• Published: New York IEEE 2021; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Coupled resonators; dielectric constant; Electric fields; Frequency measurement; liquid characterization; Liquids; Magnetic liquids; Microstrip; microwave sensor; multiband sensor; Permittivity; relative permittivity; Resonant frequencies; Resonant frequency; Resonators; Sample holders; Sensors; Substrates
• ISSN: 0018-9456; 1557-9662
• DOI: 10.1109/TIM.2021.3122116

A six-band microstrip sensor, based on a pair of electrically coupled resonators (ECRs), is proposed to perform multifrequency dielectric characterization of liquids. A pocket is milled through the substrate bottom of the sensor to contain the fluid sample, avoiding the need for a sample holder. The pocket has been designed to achieve a higher electric field magnitude in the sensing region and a mechanism to separate the resonant frequencies, which helps to ensure a high span between the first and the last resonant frequency. The microstrip sensor is implemented on a 1.905-mm-thick substrate with <inline-formula> <tex-math notation="LaTeX">\varepsilon ^{\prime }_{r} = 12.2 </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">\tan \delta = 0.0019 </tex-math></inline-formula>. The sensor's six resonance frequencies span the range between 1 and 3.5 GHz. Experimental tests show that the sensor can measure a wide range of <inline-formula> <tex-math notation="LaTeX">\varepsilon ^{\prime }_{r} </tex-math></inline-formula> values between 2 and 79 resulting in close similarities to the dielectric constants published in previous works.