Huang, Xiaobo. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 108-111). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Recent developments in digital communications at microwave frequencies have revealed that local oscillator phase noise is often a factor in the bit error rate (BER) analysis. Digital signals transported across microwave radio links acquire waveform jitter from local oscillator phase noise. As jitter increases so does BER. The main goals of the investigations described in this dissertation are to demonstrate the feasibility of determining rms jitter from measured phase noise and to develop mathematical models to describe how local oscillator phase noise is added to an information signal passing through a radio link. The first goal of estimating jitter from phase noise data has many applications. An obvious use is to specify the phase noise performance of a local oscillator for a given jitter specification which in turn may be specified for a desired BER level. A less obvious application is the ability to estimate the jitter of a microwave or millimeter wave signal based on measured phase noise. At these high frequencies it is often impractical or impossible to measure jitter directly due to performance limitations of time domain equipment such as the digital sampling oscilloscopes (DSO) which are typically limited to about 22 GHz. Conversely spectrum analysis techniques are well developed that allow accurate phase noise measurements to be performed well beyond 100 GHz. Experiments which validate the known relation between an oscillator's single sideband phase noise and associated mean square jitter [8, 28] are presented. Test equipment was developed to allow the addition of phase noise in a controlled manner to a clean reference signal which for practical purposes has no inherent jitter. By performing the experiments at the relatively low frequency of 33.333 MHz both the phase noise and jitter could be measured easily. Comparing the rms jitter predicted from phase noise data to direct measurement with a Digital Sampling Oscilloscope determined that the relation gave typically less than 14% error with a worst case disagreement of 24%. The experiment had an estimated uncertainty of �� 17%. This level of agreement is acceptable for many BER applications, which often specify jitter to an order of magnitude. The second goal of the research was to develop a model which describes how the phase noise of transmitter and receiver local oscillators add to an information signal carried over a communications link. It is shown that this added phase noise can in principle be eliminated in a double sideband communications system when the relative phase difference between the two local oscillators is synchronized to N��, where N is any integer. Experiments were performed which validated the predicted results. It was found that using real components allowed a 24 dB reduction added phase noise when compared to the case when no synchronization was used. A practical circuit is proposed to implement the technique in a practical manner for real radio systems. A final area of research presented phase noise measurements for a Gunn diode microwave integrated circuit (MIC) voltage controlled oscillator (VCO) in the 18 GHz region. The single sideband phase noise ratio of -96 dBc/Hz at 100 kHz offset frequency was significantly better than current published data for MESFET, HBT, and PHEMT VCOs at similar frequencies. These results are important in the area of digital radios, since improved phase noise allows higher data rates and reduces adjacent channel power. / Graduation date: 1999

Thesis (M.S.)--Montana State University--Bozeman, 2006. / Typescript. Chairperson, Graduate Committee: James P. Becker. Includes bibliographical references (leaves 120-121).

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references (leaves 152-167). Also available in electronic version.

An improved physically-based rainfall algorithm was developed using AMSR-E data based on a radiative transfer model. In addition, error models were designed and embedded in the algorithm to assess retrieval errors quantitatively and to reduce net retrieval uncertainties. The algorithm uses six channels (dual polarizations at 36.5, 18.7 and 10.65GHz) and retrieves rain rates on a pixel-by-pixel basis. Monthly rain totals are estimated by summing average rain rates computed by merging six rain rates based on proper weights that are estimated from error models. Error models were constructed based upon the principal error sources of rainfall retrieval such as beam filling error, drop size distribution uncertainty and instrument calibration errors. Several improved schemes that minimize uncertainties of the rainfall retrieval were developed in this study. In particular, improved offset correction that corrects the biases near zero rain plays a very important role for reducing uncertainties which are mainly driven by calibration uncertainty including the modeling errors. AMSR-E's larger calibration uncertainty was substantially absorbed by this offset correction as well as by the weighted average scheme to combine all six channels optimally. As a framework for inter-comparison with the experimental algorithm, the current operational algorithm (NASA, level 3 algorithm) was also updated with respect to AMSR-E data. The experimental algorithm was compared with the operational algorithm for both AMSR-E and TMI data and rainfall retrieval uncertainties were analyzed using error models. When the experimental algorithm was used, many limitations of the operational algorithm were overcome and uncertainties of rainfall retrieval were considerably eliminated.

In recent years, the upstream oil and gas industry has dealt with some of the most challenging metering applications. One of these is the measurement of water percentage at the point of allocation. It is an essential requirement when test separators or the newly developed full multiphase meters are utilized for oil well production testing. Water-cut can be obtained from measurement of differential pressure, capacitance/conductance, gamma rays absorption, absorption of infrared light, coriolis mass measurement, or microwave permittivity. The use of microwave permittivity has been shown to be very effective with the added benefit of not requiring a nuclear source, as is the case with a gamma ray densitometers. A common problem encountered in oil well production testing is that of gas “carry-under” into the liquid stream exiting the test separator. This results in a trace amount of gas entering the water-cut meter, producing errors in the water-cut reading. Gas carry-under may be caused by high liquid viscosity, improper separator operation, or poor separator design. Gas carry-under is believed to be one of the major causes of large allocation factors in oil and gas operations. Problems in clearly defining the three-phase stream as to flow regime and actual gas bubble size have been described in the technical literature. Pertinent references are discussed and compared. The issues in trying to perform such tests in the laboratory and the correlation of the data are disclosed and the difficulties in trying to correlate the effects of the entrained gas are described. Field testing and experience by at least one manufacturer of equipment has verified the effect of entrained gas, but little quantitative data relating gas-cut to increased error of measurement has been published. The objective of this work was to investigate the performance of a microwave water-cut analyzer under three-phase flow conditions to determine the impact of the presence of gas in the liquid stream. Experiments were performed that investigated the effects of entrained gas on a commercial water-cut analyzer. These tests were conducted at the Texas A&M Tommie E. Lohman Fluid Measurement Laboratory at low pressure conditions (< 40 psig). The test fluids were air, water and two types of oil: mineral oil and hydraulic oil. These experiments investigated oil continuous emulsion conditions with the Gas Volume Fraction (GVF) ranging from 0-25% and the water-cut ranging from 5-30%. Liquid flow rates were between 500-3,700 bbl/day. A 2-inch water-cut full range meter was utilized for these tests. The error in water-cut was seen to increase with increasing GVF ranging from 0% to 25%. However, the measurement remained stable over the entire range of tests. A correction was developed to correct water-cut meter readings based on the amount of gas in the liquid stream.

Free-space imaging with a resolution beyond that dictated by the classical diffraction limit may be achieved with a `Veselago-Pendry' superlens made from a metamaterial possessing a number of specific properties, including a negative refractive index (NRI). Although a planar NRI transmission-line (NRI-TL) metamaterial based on the periodic lumped loading of a host TL network has successfully verified the phenomenon of superlensing in a 2D microstrip environment, a true Veselago-Pendry superlens capable of interacting with and manipulating fields in free space remained elusive, largely due to the difficulty of meeting its stringent design constraints and also to the problem of realizing a full 3D isotropic, polarization-independent structure. This work presents the first experimental verification of free-space Veselago-Pendry superlensing using a new class of volumetric metamaterials based on 2D NRI-TL layers that, although polarization-specific, may be easily constructed using available lithographic techniques to interact with free-space sources. An equivalent-circuit model is developed to enable accurate design of the metamaterial's dispersion and transmission characteristics, including those associated with Veselago-Pendry superlensing, and is validated using full-wave simulations. First, a volumetric NRI-TL metamaterial employing fully printed loading elements is fabricated to verify the salient properties of a free-space metamaterial-slab lens. This lens demonstrates diffraction-limited focusing at X-band and, thus, affirms theoretical results that suggest that electrically thick and lossy metamaterials are unable to perform superlensing. Thereafter, a volumetric NRI-TL metamaterial based on discrete lumped elements is designed to meet the conditions of the Veselago-Pendry superlens at 2.40GHz, and experimentally demonstrates a resolution ability over three times better than that afforded by the classical diffraction limit. A microwave superlens designed in this fashion can be particularly useful for illumination and discrimination of closely spaced buried objects over practical distances by way of back-scattering, for example, in tumour or landmine detection, or for targeted irradiation over electrically small regions in tomography or hyperthermia applications. Possible optical implementations of the volumetric topology are also suggested, and finally, a fully isotropic, polarization-independent 3D metamaterial structure related to the volumetric NRI-TL structure is proposed.

Free-space imaging with a resolution beyond that dictated by the classical diffraction limit may be achieved with a `Veselago-Pendry' superlens made from a metamaterial possessing a number of specific properties, including a negative refractive index (NRI). Although a planar NRI transmission-line (NRI-TL) metamaterial based on the periodic lumped loading of a host TL network has successfully verified the phenomenon of superlensing in a 2D microstrip environment, a true Veselago-Pendry superlens capable of interacting with and manipulating fields in free space remained elusive, largely due to the difficulty of meeting its stringent design constraints and also to the problem of realizing a full 3D isotropic, polarization-independent structure. This work presents the first experimental verification of free-space Veselago-Pendry superlensing using a new class of volumetric metamaterials based on 2D NRI-TL layers that, although polarization-specific, may be easily constructed using available lithographic techniques to interact with free-space sources. An equivalent-circuit model is developed to enable accurate design of the metamaterial's dispersion and transmission characteristics, including those associated with Veselago-Pendry superlensing, and is validated using full-wave simulations. First, a volumetric NRI-TL metamaterial employing fully printed loading elements is fabricated to verify the salient properties of a free-space metamaterial-slab lens. This lens demonstrates diffraction-limited focusing at X-band and, thus, affirms theoretical results that suggest that electrically thick and lossy metamaterials are unable to perform superlensing. Thereafter, a volumetric NRI-TL metamaterial based on discrete lumped elements is designed to meet the conditions of the Veselago-Pendry superlens at 2.40GHz, and experimentally demonstrates a resolution ability over three times better than that afforded by the classical diffraction limit. A microwave superlens designed in this fashion can be particularly useful for illumination and discrimination of closely spaced buried objects over practical distances by way of back-scattering, for example, in tumour or landmine detection, or for targeted irradiation over electrically small regions in tomography or hyperthermia applications. Possible optical implementations of the volumetric topology are also suggested, and finally, a fully isotropic, polarization-independent 3D metamaterial structure related to the volumetric NRI-TL structure is proposed.

Disinfestation using microwaves can be an alternate to chemical methods of killing insects in grain. A pilot-scale industrial microwave dryer operating at 2.45 GHz was used to determine the mortality of life stages of Tribolium castaneum (Herbst), Sitophilus granarius (L.) and Cryptolestes ferrugineus (Stephens) adults in wheat, barley, and rye. Grain samples of 50 g each at 14, 16, and 18% moisture content were infested with stored-grain insects. The samples were then exposed to microwave energy at 200, 300, 400, and 500 W for exposure times of 28 and 56 s. Complete (100%) mortality was achieved for adults of three insect species at 500 W, 28 s and at 400 W, 56 s in barley and wheat. In rye, complete mortality of adult T. castaneum and S. granarius was achieved at 400 W, 28 s and at 300 W, 56 s whereas for C. ferrugineus, complete mortality was achieved at 500 W, 28 s and at 400 W, 56 s. The average temperature of wheat, barley, and rye at 500 W and 28 s was around 80, 71 and 82oC, respectively, and moisture loss was 2.0, 1.9 and 2.5 percentage points, respectively. Among the life stages of T. castaneum in wheat, eggs were the most susceptible followed by larvae, and the least susceptible were the pupae and adults. Among the life stages of T. castaneum in barley and rye, eggs were the most susceptible and adults were the least susceptible with no significant difference between pupae and larvae. There was no significant difference in the mortality of adults at 14, 16, and 18% moisture content barley and rye and the life stages of T. castaneum and S. granarius in rye. Germination of seeds decreased with an increase in power level or exposure time or both. There was no significant difference in the quality characteristics of microwave-heated wheat and rye except for reduced flour yield in rye. The quality of the barley treated at 500 W, 28 s was the same as the control, whereas, there was significant decrease in the quality of barley treated at 400 W, 56 s. / May 2009

<p>In this thesis, a 3D microwave imaging method is developed for a microwave imaging system with an arbitrary background medium. In the previous study on the breast cancer detection of our research group, a full wave inverse method, the Diagonal Tensor approximation combined with Born Iterative Method (DTA-BIM), was proposed to reconstruct the electrical profile of the inversion domain in a homogenous background medium and a layered background medium. In order to evaluate the performance of the DTA-BIM method in a realistic microwave imaging system, an experimental prototype of an active 3D microwave imaging system with movable antennas is constructed. For the objects immersed in a homogenous background medium or a layered background medium, the inversion results based on the experimental data show that the resolution of the DTA-BIM method can reach finely to a quarter of wavelength of the background medium, and the system's signal-noise-ratio (SNR) requirement is 10 dB. Moreover, the defects of this system make it difficult to be implemented in a realistic application. Thus, another active 3D microwave imaging system is proposed to overcome the problems in the previous system. The new system employs a fix patch antenna array with electric switch to record the data. However, the antenna array makes the inversion system become a non-canonical inhomogeneous background. The analytical Greens' functions used in the original DTA-BIM method become unavailable. Thus, a modified DTA-BIM method, which use the numerical Green's functions combined with measured voltage, is proposed. This modified DTA-BIM method can be used to the inversion in a non-canonical inhomogeneous background with the measured voltages (or $S_{21}$ parameters). In order to verify the performance of this proposed inversion method, we investigate a prototype 3D microwave imaging system with a fix antenna array. The inversion results from the synthetic data show that this method works well with a fix antenna array, and the resolution of reconstructed images can reach to a quarter wavelength even in the presence of a strongly inhomogeneous background medium and antenna couplings. A time-reversal method is introduced as a pre-processing step to reduce the region of interest (ROI) in our inversion. In addition, a Multi-Domain DTA-BIM method is proposed to fit the discontinue inversion regions. With these improvements, the size of the inversion domain and the computational cost can be significantly reduced, and make the DTA-BIM method more feasible for rapid response applications.</p> / Dissertation