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In this paper, a microwave sensor with a meandered microstrip structure is introduced to measure the permittivity of the various liquids. The performance of the sensor is based on the change of operating resonance frequency during the absence and presence of materials in the sensing area. In this study, liquids including ethanol, methanol, aqueous glucose solution, and deionized water have been selected as samples under test. The proposed sensor has been implemented on RO4003 substrate with dimensions of 35 × 20 × 0.508 mm3 and operating frequency of 6.21 GHz in a free load state with a Q-factor of 506. When the samples are present in the sensing area, the frequency of the sensor shifts from 5.42 to 3.27 GHz. The sensitivity of 0.64% is obtained for the presented sensor. Compact size, linearity of changes, and low cost are the most important advantages of the sensor. The introduced sensor can be used in various fields of industrial, medical, and diagnostic due to its performance. [ABSTRACT FROM AUTHOR]

This paper introduces a symmetric bar chart-shape (SBCS) microwave sensor for measuring permittivity of fluidic samples. For designing purposes, the introduced sensor was used based on the field changes between the SBCS and rectangular loop microstrip (RLM) structure. When a sample is placed on the sensing location, interaction between SBCS and RLM varies the field intensity. The vinegar samples were combined with water and then they are placed on the sensor. The change in field intensity changes the resonance frequency. However, there is a relationship between the permittivity of samples and the resonance frequencies. The proposed sensor is implemented on the substrate of RO4003C. The relative permittivity of samples changed from 59 to 77 and the resonance frequencies changed from 2.3 to 1.4 GHz. The quality factor is 3544 and the sensitivity is 2.2%. [ABSTRACT FROM AUTHOR]

Summary: In this paper, a microwave sensor is designed and built to measure the permittivity of aqueous solutions. The samples used in this experiment are different purities of ethanol mixed with water. Ethanol solution with different purities is a widely used material in industry. Structures of meander, ladder, and T‐structure were used to design the sensor. Then the designed sensor is simulated in CST software in range of relative dielectric from 10 to 80. After obtaining the desired answer in the simulation, the proposed sensor is built on the Rogers 4003 substrate, the built‐in sensor measured ethanol solution with a purity of 5% to 35% (equivalent to permittivity of 76 to 58), and is showed a sensitivity of 4% and a Q‐factor of 3500. The results of simulation and measurement are consistent with each other, and they indicated that the proposed sensor beyond the fluids can be supported and determine their relative dielectrics. [ABSTRACT FROM AUTHOR]

In this paper, the human milk dielectric constant by a microwave sensor has been evaluated. The proposed sensor is result of coupling between a simple microstrip line and a split ring resonator and its resonance frequency is 6 GHz. When up to 30 μl of milk are placed on the sensing area on the sensor, it causes the resonance frequency to shift. Six samples of human milk were measured by a network analyzer, then the dielectric constant of the samples were determined, and three similar samples were measured by the built‐in sensor. The proposed microwave sensor has Q‐factor of 38 and its sensitivity is 0.17%. The implemented sensor has acceptable performance compared to previous sensors and it can be used to determine the normal behavior of human milk with a simple method and for this work, it requires to small value of sample for measurement. Key Points: The proposed sensor is able to measure of the milk sample up to a volume of 30 μlTypes of milk including human and animal can be measured by the proposed sensorThe Q‐factor and sensitivity of the sensor is acceptable compared to previous works [ABSTRACT FROM AUTHOR]

• Microwave sensor based on the split ring resonator has been proposed. • Detection of ε′ for two different liquid samples at two separate frequencies. • Detection of permittivity of one sample at two frequency bands. • The considered sensor advantages are high Q-factor, high sensitivity and compact. • Measuring of changes in glucose concentration in blood in the medical industry. In this paper, a microwave sensor based on the split ring resonator has been proposed to detect the real part of the dielectric constant of the liquid sample. The proposed structure composed of non-identical double-split ring resonators which are placed in the inner part of the power divider branches. The proposed sensor has two purposes: (1) Measurement of the permittivity of one sample under test in two frequency bands (multi-band), (2) Dual samples under test for simultaneous dielectric detection (multi-sensing). There are several advantages in measuring the permittivity of the sample under test with the proposed sensor such as high Q-factor, high sensitivity, compact size, multi-sensing and multi-band. This paper investigates resonance frequency variation relative to the samples with different permittivities, such as ethanol, methanol, glucose solution and deionized water compared to previous similar works in simulation and experimental results. The permittivity of samples under test varies from 24 to 78 at 25 ˚C, and the simulated sensor resonance frequency would change about from 5.76 to 4.8 GHz at first resonance frequency and 7.85 to 6.35 GHz at second resonance frequency. [ABSTRACT FROM AUTHOR]