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Advances in Active Resonator based Planar Microwave Sensors for Material Characterization
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- Author / Creator
- Abdolrazzaghi, Mohammad
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Microwave planar resonators have been used for material characterizations for the past two decades. Among the many advantages from planar sensors, some of the main drawbacks are discussed and the relevant methods are provided to tackle them through this thesis. Generally, unique characteristics of microwave sensors such as the ability to perform non-intrusive real-time measurements makes them very appealing for chemical characterization. This becomes more interesting for harsh environment as it has very simple interface. Inherent associated challenges in microwave resonant based sensing are sensitivity and selectivity. Recently, the sensitivity issue has been addressed in our group to eliminate such problem by developing high resolution microwave sensors. In this thesis, we focus on advancing such sensors and further investigating their sensitivity and selectivity related challenges. To design high resolution sensor a passive microwave resonator is embedded within a regenerative circuit to provide negative resistance and remove the loss of the system. The resultant high-quality factor sensor is able to track highly sensitive measurements such as Nano-particles, e.g. Asphaltene based model-oils. In this study, precipitation and deposition of the Asphaltene at 1.2 GHz is measured and showed that it is concentration-dependent when mixed with a precipitant element, e.g. n-Heptane here. In the second step, two pairs of ultra-wideband high gain slot bow-tie antenna are exploited to accompany the sensor and remove any wired connection with the measuring device. Single-layered antennas are designed to offer 5dB gain over the bandwidth of 1.35-2 GHz, with whose installation, the quality factor of the sensor becomes Q ≈22000. Common chemicals such as IPA, acetone, ethanol, methanol, and water are analyzed with wireless communication. Salt-water wall with concentration of 0.003125 g/ml – 0.1 g/ml is used as the lossy medium, and the sensor’s bare response could also be captured.In the next step, the unwanted environmental impacts on sensing are considered as erroneous factors needed to be removed for robust measurements. Hence the single active resonator is developed into dual active sensor with enhanced functionality in tracking environmental effects. Dual uncoupled active Split Ring Resonators (SRRs), are enhanced in Q-factor from 51 and 54 up to 150k and 210k at 1.365 GHz and 1.6 GHz, respectively. The effect of humidity in sensing material under test (MUT) is calibrated out and more reliable sensing characteristics can be evaluated regardless of the uncontrollable ambient conditions. Based on the proposed technique, root of mean-square-error of processed results of measuring water in humid air was significantly reduced from 169k down to 27k. Common liquids are detected within moist sand environment successfully and the material impact is completely distinguished from that of the moist sand. It is also shown that the dual active resonator can be used in unique configuration for other applications, for instance to analyze the dispersion coefficient (k) of Nano-particle suspensions inside solutions. The measured k for Asphaltene in Heptane is consistent with the values reported in the literature. Dispersion of Asphaltene Nano-Particles in n-Heptane is measured in wide range of 0.000625-0.625 (%wt) Asphaltene : Toluene. Dual active resonator is designed at independent frequencies of 1.03 GHz (fL) and 1.149 GHz (fH). With the frequency shifts (ΔfL, ΔfH), average flow rate, and the inner diameter of the tube, the molecular diffusion coefficient, and then the dispersion coefficient can be rapidly derived according to two-window solution of Taylor-Aris dispersion analysis. Samples with higher concentration of Asphaltene are shown to have faster spread and larger dispersion in the flow. Dispersion coefficients of the samples cover the range of 5.2 -7 -4 2 ×10 mm /s in great agreement with conventional methods. In the last impactful attempt to improve the sensitivity of the sensor, mixing behavior of the sensor in its oscillatory mode is exploited, where it’s output combined with an additional signal is shown to produce intermodulation products. Intermodulation (IM) of the sensor’s two independent sources in this configuration magnifies the variations in the sensing element arbitrarily and commensurately with IM product order. The resulting structure, then provides sensitivity much larger than the primary signal. The improvements are all into effect in the final design of mixer-based sensor where wireless communication is also applied. Common fluids such as Toluene, IPA, Methanol, and Water are tested in fluidic channel and demonstrated that the sensitivity for intermodulation products are significantly increased.
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- Graduation date
- Fall 2017
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- Type of Item
- Thesis
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- Degree
- Master of Science
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- License
- This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.