Design of a High Sensitivity Microwave Sensor for Liquid Dielectric Constant Measurement

Abstract

In order to improve the sensitivity of liquid dielectric constant measurements, a liquid dielectric constant sensor based on a cubic container structure is proposed for the first time. The cubic container, which consists of a dielectric substrate with a split resonant ring (SRR) and microstrip lines, can enhance the electric field intensity in the measuring area. High sensitivity can be obtained from measuring the dielectric constant with the characteristics of the structure resonate. The research results show that the resonant frequency of the sensor is shifted from 7.69 GHz to 5.70 GHz, with about a 2 GHz frequency offset, when the dielectric constant of the sample varied from 1 to 10. A resonance frequency offset of 200 MHz for the per unit dielectric constant is achieved, which is excellent regarding performance. The permittivity of oil with a different metal content is measured by using the relation between the fitted permittivity and the resonant frequency. The relative error is less than 1.5% and the sensitivity of measuring is up to 3.45%.

Differential Microstrip Sensor for Complex Permittivity Characterization of Organic Fluid Mixtures

“…Resonating sensors are widely used in different applications such as: solid dielectric characterization [ 1 , 2 , 3 ], biomedical application [ 4 , 5 ], permittivity measurements for liquid mixtures [ 6 , 7 , 8 ], or even characterization of soil water content [ 9 , 10 ]. Generally, the most used are planar sensors due to their low cost, low profile, easy fabrication, high precision, robustness, and compact size [ 11 ].…”

Graphene based T‐shaped monopole antenna sensor for food quality evaluation

“…[28][29][30] The proposed antenna sensor shows a high sensitivity of 460 MHz. The quality factor (Q-factor) of the proposed antenna sensor is calculated as 157 depending upon the resonant frequency and bandwidth of the proposed sensor using the formula: [31][32][33]…”

Comparison of the Moist Material Relative Permittivity Readouts Using the Non-Invasive Reflectometric Sensors and Microwave Antenna

“…The real part describes the baseline value of moisture estimation using dielectric techniques, namely the amount of energy released in the alternating field, and the imaginary part includes energy losses due to ionic conductivity, which are strongly dependent on material salinity [ 42 ]. The complex relative permittivity of a lossy medium can be calculated according to the following extended formula [ 32 , 41 , 43 , 44 , 45 , 46 ]: where ε ′ r denotes the real part of relative permittivity of medium, ε ″ r the imaginary part of relative permittivity of medium, i the imaginary unit ( i 2 = −1), σ 0 the electrical conductivity [S/m], ε 0 the permittivity of vacuum ( ε 0 = 8.85 × 10 −12 F/m), and ω the angular frequency of the external electric field [rad/s].…”