Al-Hegazi, Ammar Abdullah Hussein (2024) New microwave sensor with high quality factor for liquid characterization using gap waveguide resonator. Doctoral thesis, Universiti Teknikal Malaysia Melaka.
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Abstract
Characterization of material properties is crucial for facilitating a wide range of industrial applications, notably in food processing, bioengineering, and the pharmaceutical industry. Each material exhibits specific electrical behaviors influenced by its dielectric properties. Traditionally, material characterization has been conducted using conventional waveguides, such as rectangular waveguide cavities and horn antenna waveguides. However, these traditional resonators are typically large and complex to manufacture. Consequently, most researchers prefer planar structures, such as microstrip structures, for material sensing due to their simplicity and low cost. Despite these advantages, planar resonators are susceptible to external factors like oxidation and electromagnetic (EM) waves, leading to low sensitivity and Q-factor. Moreover, most microwave sensors are limited to detecting changes in liquid mixtures only when the changes exceed 10%; smaller changes go undetected. In response to these challenges, this research proposes a new microwave sensor with high sensitivity and quality factor, based on a gap waveguide resonator operating at 5.8 to 6.2 GHz for liquid characterization. Different types of liquids are analyzed and evaluated both in electromagnetic simulations and laboratory experiments using the proposed gap waveguide sensor (GWS). The gap waveguide was chosen for its ability to effectively concentrate the electric field, resulting in a high quality factor (Q-factor) and enhanced sensitivity. The liquid under test (LUT) is positioned in the region where the electric field is concentrated, allowing interaction between the electric field and the liquid material according to the principles of perturbation theory. The equations for the dielectric properties of the unknown LUT are extracted using the polynomial fitting method and Cramer's rule. The proposed sensor is simulated using Computer Simulation Technology (CST) and fabricated with a CNC machine. Experimental measurements and validation of the proposed sensor are performed in the laboratory using a Vector Network Analyzer (VNA) and the dielectric probe from Keysight. These measurements revealed a notably high quality factor of 6016. Various liquid materials, including chemical solutions and oils, were tested using the proposed sensor. The results demonstrated the sensor's remarkable sensitivity, capable of detecting even 1% changes in the mixture of ethanol and distilled water. A comparison between simulated and measured outcomes indicated strong agreement between the two data sets. The experiment showed that the proposed sensor could differentiate between different types of oils, such as virgin oil, light oil, pure oil, and used oil. The measurements using the proposed sensor showed good agreement with the dielectric probe from Keysight Technologies, with an accuracy of up to 99.65%. A comparison between the proposed sensor and recently reported research indicated that the proposed sensor has the highest quality factor. Therefore, the proposed sensor is reliable and a strong candidate for industrial applications, such as food processing, bioengineering, and the pharmaceutical industry.
| Item Type: | Thesis (Doctoral) |
|---|---|
| Uncontrolled Keywords: | Material characterization, Dielectric properties, Electrical behaviors |
| Divisions: | Library > Tesis > FTKEK |
| Depositing User: | Muhamad Hafeez Zainudin |
| Date Deposited: | 31 Jan 2025 16:28 |
| Last Modified: | 31 Jan 2025 16:28 |
| URI: | http://eprints.utem.edu.my/id/eprint/28373 |
| Statistic Details: | View Download Statistic |
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