Microwave resonant sensor for measurement of ionic concentration in aqueous solutions

Nitrate efflux from agricultural lands in the Midwestern United States mixes with surface streams and creates hypoxic conditions in the Gulf of Mexico, which lead to destruction of aquatic ecosystems. Besides, excess nitrate in drinking water poses a serious threat to human health, including blue baby syndrome, birth defects, and cancer. The current nitrate management techniques are inefficient and expensive, and a major reason for this is the lack of low-cost, effective ionic concentration monitoring systems. The dependence of nitrate concentration on local hydrology means that laboratory techniques yield incomplete data, whereas the available real-time monitoring techniques have drawbacks like exorbitant cost, ion selectivity issues, and others. This research aims to bridge the gap between reliable concentration monitoring and economic feasibility by developing a low-cost, effective, real time ion monitoring system which is field deployable and sensitive to changes in ionic concentration at agriculturally-relevant levels. In this work, a resonant sensor is designed using an open-ended coaxial transmission line which can be evanescently perturbed by a liquid sample and shows a shift in its resonant frequency on change of ionic concentration of the sample. The dimensions of the coaxial resonator are optimized to ensure high sensitivity to changes in the ionic concentration of the sample at relevant concentrations, low manufacturing costs, and small physical dimensions to enable field deployment. The resonant sensor design is followed by the design and optimization of a suitable coupling structure which can take two-port transmission measurements to measure the characteristics of the resonator. Finite Element Analysis (FEA) simulations are carried out using ANSYS HFSS, using as input data the complex permittivity of aqueous solution samples with varying concentrations of nitrate, sulfate, and chloride ions. Deionized water is taken as a reference sample, and a clear correlation between shift in resonant frequency and ionic concentration is observed for each of the three resonant modes studied, with the sensor being highly sensitive to concentration changes at agriculturally relevant concentrations. Appropriate fitting functions are implemented to represent the correlations between resonant frequency and ion concentration, and discussion on the feasibility of the designed sensor for field deployment is presented

Microwave emissions from snow

The radiation emitted from dry and wet snowpack in the microwave region (1 to 100 GHz) is discussed and related to ground observations. Results from theoretical model calculations match the brightness temperatures obtained by truck mounted, airborne and spaceborne microwave sensor systems. Snow wetness and internal layer structure complicate the snow parameter retrieval algorithm. Further understanding of electromagnetic interaction with snowpack may eventually provide a technique to probe the internal snow propertie

A millimeter-wave kinetic inductance detector camera for long-range imaging through optical obscurants

Millimeter-wave imaging provides a promising option for long-range target detection through optical obscurants such as fog, which often occur in marine environments. Given this motivation, we are currently developing a 150 GHz polarization-sensitive imager using a relatively new type of superconducting pair-breaking detector, the kinetic inductance detector (KID). This imager will be paired with a 1.5 m telescope to obtain an angular resolution of 0.09° over a 3.5° field of view using 3,840 KIDs. We have fully characterized a prototype KID array, which shows excellent performance with noise strongly limited by the irreducible fluctuations from the ambient temperature background. Full-scale KID arrays are now being fabricated and characterized for a planned demonstration in a maritime environment later this year

Microwave measurement techniques for industrial process monitoring and quality control

Process monitoring and quality control by sensor measurements are essential for the automatisation and optimisation of many industrial manufacturing processes. This thesis is concerned with microwave sensing, which is a measurement modality with potential to improve the in-line sensing capabilities in several industries. Two process-industrial measurement problems are considered that involve the estimation and detection of permittivity variations for granular media in a fluidised or flowing state. For these problems, we present microwave measurement techniques based on resonant cavity sensors, accounting for the electromagnetic design and modelling of the sensor, signal processing algorithms, and experimental evaluation in relevant industrial settings. These measurement techniques make simultaneous use of multiple resonant modes with spatial diversity to improve the measurement capabilities. Furthermore, we exploit model-based signal processing algorithms where knowledge of the underlying physics is utilised for improved estimation and detection.The first problem is to monitor the internal state of a pharmaceutical fluidised bed process used for film-coating and drying of particles. The metal vessel that confines the process is here treated as a cavity resonator and the complex resonant frequency of eight different cavity modes are measured using a network analyser. Based on the resonant frequencies, we estimate parameters in a low-order model for the spatial permittivity distribution inside the vessel, which can be related to process states such as the liquid and solid content of the particles in different regions.The second measurement problem is an aspect of quality control, namely the detection of undesirable objects in flowing granular materials. We present measurement techniques based on resonant cavity sensors that are capable to detect the presence of small dielectric objects embedded in a flowing granular material. Detection algorithms that exploit the statistics of the noise caused by material density fluctuations and the characteristic signatures caused by an object passage event, are evaluated based on experiments which lead to quantitative assessments of the detection performance

Thermometry based on Whispering Gallery Mode resonators

Whispering gallery (WG) mode resonators were studied since 1980s for precision clock oscillators and for cavity quantum electrodynamics studies. They are a kind of stable, high Q, microwave resonators where a symmetric dielectric medium, such as a cylinder or a disk, is suspended in the centre of a metal cavity. A coaxial cable or a waveguide are used to couple the EM field in the microwave region and thus to excite the system resonant frequencies. WG modes are resonant modes of higher-order azimuthal number (m) having most of the EM energy concentrated on the dielectric surface. Within the temperature range of -196 °C to 500 °C the most commonly used industrial thermometer is platinum resistance thermometer (PRT) with the uncertainties of 10 mK. The PRT offers high accuracy, low drift, a wide operating range; however, it is very sensitive to mechanical shock in handing and shipping. Besides, an AC resistance bridge which is typically required as a readout device for PRT is very expensive. Accordingly, there is a great need for a stability-improved, resistant to mechanical shock, potential lower uncertainty and cost-effective industrial thermometer. WGMR thermometer (WGMRT) is a new kind of thermometer which offers greater vibration immunity, improved stability, smaller uncertainty in temperature measurement and potential lower cost than platinum resistance thermometry. An innovative sapphire whispering gallery thermometer (SWGT) was first explored at the National Institute of Standards and Technology (NIST) in 2007 by Strouse [1] with the uncertainty less than 10 mK. Five WGMs with nominal resonant frequencies ranging from 14.4 GHz to 19.1 GHz and with Q-factors, respectively, ranging from 20,000 to 90,000 were measured within the temperature range of 0 °C to 100 °C. The accuracies of his WGMTs were in the range of ± 0.02 °C and ice point repeatability was better than 2 mK. The thesis reports the tests performed on several WGMR thermometers which have different shapes of crystals to evaluate their stability, resolution and repeatability in the temperature range of -40 °C to 85°C. Thermal cycle experimental results IV showed a Q in excess of 100000 for the mode with the highest azimuthal number, making it possible to achieve a potential temperature resolution of 0.1 mK. Besides, different specimens of crystals with the same nominal specification and reassemble for the same specimen were both tested to check the reproducibility of the thermometer. The birefringence of the sapphire was also studied to make an innovative thermometer. The ratios of two doublet frequencies are sensitive to the temperature-dependent birefringence of the crystal and relatively insensitive to surface contamination and changes in the shape of the cavity. Besides, it can have an external shape that closely approximates the shape of conventional platinum resistance thermometer

Analytical and Experimental Methods for the Characterization of Field Propagation in Non-Standard Conditions

The electromagnetic propagation is totally and fully assessed in free space, in standard working conditions. However there exists peculiar propagation environments in which the propagation has not been studied but in which it could be fully exploited in order to assess specic needs or to provide new sensing tools. In particular the research activity describes in this thesis has been devoted to the study of the propagation in non-standard condition

Electromagnetic Wave Theory and Applications

Contains table of contents for Section 3 and reports on five research projects.U.S. Department of Transportation Contract DTRS-57-88-C-00078TTD13U.S. Department of Transportation Contract DTRS-57-88-C-00078TTD30Defense Advanced Research Projects Agency Contract MDA972-90-C-0021Digital Equipment CorporationIBM CorporationJoint Services Electronics Program Contract DAAL03-89-C-0001Joint Services Electronics Program Contract DAAL03-92-C-0001Schlumberger-Doll ResearchU.S. Navy - Office of Naval Research Grant N00014-90-J-1002U.S. Navy - Office of Naval Research Grant N00014-89-J-1019National Aeronautics and Space Administration Grant NAGW-1617National Aeronautics and Space Administration Grant 958461National Aeronautics and Space Administration Grant NAGW-1272U.S. Army Corp of Engineers Contract DACA39-87-K-0022U.S. Navy - Office of Naval Research Grant N00014-89-J-110

A millimeter-wave kinetic inductance detector camera for long-range imaging through optical obscurants

Millimeter-wave imaging provides a promising option for long-range target detection through optical obscurants such as fog, which often occur in marine environments. Given this motivation, we are currently developing a 150 GHz polarization-sensitive imager using a relatively new type of superconducting pair-breaking detector, the kinetic inductance detector (KID). This imager will be paired with a 1.5 m telescope to obtain an angular resolution of 0.09° over a 3.5° field of view using 3,840 KIDs. We have fully characterized a prototype KID array, which shows excellent performance with noise strongly limited by the irreducible fluctuations from the ambient temperature background. Full-scale KID arrays are now being fabricated and characterized for a planned demonstration in a maritime environment later this year

Cylindrical microwave resonator sensors for measuring materials under flow

In this thesis the various possibilities of implementing microwave sensors for measureing materials flowing in pipes are studied, with special emphasis on full-bore resonator sensors. With such resonator sensors a method to confine the electro-magnetic energy in the sensor must be used. Two main principles are studied in detail, the principle of resonance below cut-off, and the design using end grids. The first principle is shown to allow sensors with fairly open, or even completely nonintrusive structures to be designed. The second often involves sectorial or semisectorial structures. The waveguide modes in sectorial and semisectorial waveguides are therefore analyzed. From the analysis of the sectorial waveguides came the idea for a new type of resonator sensor based on the principle of resonance below cut-off, the cylindrical fin resonator sensor (CFR). Various design aspects of this sensor are studied based on calculations, measurements, and simulations using the Hewlett-Packard HFSS software. A sensor suitable for measuring the composition of mixtures of hydro-carbons and water is developed based on the discussion. The sensor has a simple mechanical structure and is less expensive to manufacture than the end grid sensors. Various designs of end grids are compared based on theoretical considerations, simulations, and measurements, and recommendations for optimized designs are given. The ring grid with eight sectors and a ratio of radii of roughly 40% is shown to provide the best isolation for a given thickness of the grid. A new type of resonator sensor based on semisectorial resonance modes, is developed for measuring the mixture ratio of oil and water in an oil well deep in the ground, where the temperature and pressure are high. The sensor is designed for installation in the annulus (i.e. the annular space between the casing or liner and the production tubing in a well), where it can be used for measuring the inflow from a specific zone in a smart well. The emphasis is on matching the spatial constraints and achieving the desired frequency response, which is analyzed theoretically, simulated with the HFSS, and finally measured. A humidity sensor for harsh environments is developed. The emphasis is on the choice of resonance mode to achieve the best immunity to contamination, and on the design of the end grids. Both calculations and field tests are presented. Predicting the height of the resonance peak under changing measurement conditions is treated also on a general level in the thesis. This issue is important, when the coupling probes are designed based on results from simulations with HFSS. The accuracy of the results obtained with HFSS is studied based on observations of scatter in the results, the dependence of the results on the convergence parameter ΔS, and by comparing the calculated and measured results. It is shown that the cut-off frequency and the resonant frequency are predicted with a higher accuracy than the quality factor.reviewe

Radar Technology

In this book “Radar Technology”, the chapters are divided into four main topic areas: Topic area 1: “Radar Systems” consists of chapters which treat whole radar systems, environment and target functional chain. Topic area 2: “Radar Applications” shows various applications of radar systems, including meteorological radars, ground penetrating radars and glaciology. Topic area 3: “Radar Functional Chain and Signal Processing” describes several aspects of the radar signal processing. From parameter extraction, target detection over tracking and classification technologies. Topic area 4: “Radar Subsystems and Components” consists of design technology of radar subsystem components like antenna design or waveform design