Analytical and Experimental Study of Microwave Microstrip Resonators for Sensing Applications

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Microwave sensors , Resonator , Dielectric anisotropy , Material characterization , Inclinometer , Tilt angle meausurement , 3D print , Sensor , Microstrip
This thesis presents innovative contributions in the field of resonance-based sensors for different applications. Firstly, a new sensor utilizing two coupled-line resonators is proposed for detecting uniaxial dielectric anisotropy. The sensor enables non-destructive testing of multiple samples at two independent frequency bands. It incorporates a T-shaped structure for resonator isolation, ensuring accurate measurements and improved reliability. By implementing a two-channel measurement approach, the sensor effectively minimizes errors caused by environmental factors. Experimental results demonstrate the sensor’s capability to simultaneously test two different samples at distinct frequencies, streamlining the experimental setup and saving time and resources.Furthermore, a novel approach utilizing active S-parameters is introduced to separate even and odd modes of dual-mode coupled resonators. This separation is particularly crucial for closely aligned and strongly coupled resonance frequencies in samples. Experimental tests confirm the feasibility of using active Sparameters for mode separation, and the sensor is successfully employed to extract dielectric constants of anisotropic FR4, RO4003C, and RO3010 samples at 2.4 and 3.4 GHz. In addition to uniaxial dielectric anisotropy sensing, the thesis explores inclination measurement. A novel inclinometer is introduced, incorporating an angular half-wavelength microstrip resonator. Two support points, essential for conducting inclination variation tests, are designed and fabricated using a 3-D printer. The inclinometer demonstrates an impressive wide angle measurement dynamic range of 84° (±42◦), which can be further extended to 180° with a simple modification. Notably, this is the first microwave inclinometer to achieve such a significantly large dynamic range. Alongside this remarkable range, the sensor’s measurements reveal a sensitivity of 0.384 mm/◦ and a resolution of 0.035◦. Furthermore, a Two-Dimensional (2-D) inclinometer implemented using microstrip technology is presented. The inclinometer comprises two orthogonal resonator sensors, enabling measurement of inclination along any axis within a 2-D plane. It offers an impressive dynamic angle measurement range of at least 80° (±40◦). To maintain consistently high sensitivity throughout this range, a customized configuration is designed, ensuring the connection between the moving and fixed parts remains intact. The experimental findings exhibit a sensitivity of 0.507 mm/◦ and a resolution of 0.029◦ for the 2-D inclinometer.
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