Universidad Pontificia Comillas. Madrid (Spain)
March 6th, 2023
Summary:
This thesis focuses on two novel sensors that are designed, tested and characterized with liquid solvents. The first dielectric resonator sensor is based on a DR fed by a slot-coupling mechanism in the ground plane of a microstrip transmission line. The second sensor fed by a parallel microstrip transmission line is shielded by a metallic housing box to prevent radiation loss. The obtained devices are fully passive sensors that a radio frequency signal can interrogate. The cavity perturbation technique is used to study the impact of the liquid under test on the resonant frequency and modal distribution; full-wave simulations corroborate the theoretical results. A prototype of the first proposed sensor tuned to work in the 2.45 GHz band has been designed, manufactured and measured by different ethanol concentrations. For the second sensor, the simulated results as well as theoretical concept are studied. Furthermore, the sensor has been fabricated and tested without shield, showing high accuracy. Additionally, the thesis presents a review on the recent metamaterial-based electromagnetic sensors, particularly on the structures that integrate the metamaterials in antenna or transmission lines for their further integration in measurement instruments. The approach followed in the review is to highlight sensitivity and quality factor (Q-factor) as they are crucial parameters in any sensor. For more insight into the metamaterial- inspired sensors, an open complementary split ring resonator (OCSRR)-loaded monopole antenna is used as a liquid sensor for discrimination of ethanol solvents with different concentrations. The sensor part is integrated with the electronic parts including a voltage-controlled oscillator (VCO) and a zero-biased Schottky Diode Detector (SDD) allowing the sensor to be low cost and portable. Indeed there are some limitations on the sensitivity level of Metamaterial-inspired sensors and saturation level of sensing by increasing the liquid percentage in the solvent under test. Consequently, the approach toward the DR sensors is much beneficial to higher sensitivity and less loss as followed in this thesis.
Descriptors: Technological Sciences, Electronic technology, Circuit design
Citation:
M. Gholami Mayani (2023), Highly sensitive microwave sensors for liquid dielectric characterization. Universidad Pontificia Comillas. Madrid (Spain).
