Recent research has shown that the Pareto family of distributions provides suitable intensity models for high resolution X-band maritime surveillance radar clutter. In particular, the two parameter Pareto Type II model has been shown to fit the Australian Defence Science and Technology Group's medium to high grazing angle clutter returns very well. The Pareto Type II model is a special case of a Burr distributional model, which is a three parameter power law statistical model. Hence this paper begins by investigating the fitting of the Burr model to real data. Based upon these results a detailed study of the development of non-coherent sliding window detectors is justified, for operation in such clutter. Several different approaches will be applied to construct the decision rules. These include a transformation approach and direct adaptation of such detectors, designed for operation in exponentially distributed clutter, to the Burr clutter setting. In addition to this, the fact that the Burr distribution is invariant with respect to two of its distributional parameters allows specication of detection processes which have the constant false alarm rate property with respect to these model parameters. Performance analysis, in simulated clutter, of the derived detectors is then examined. This includes performance in the presence of interference and false alarm regulation during clutter power transitions. This is complemented by an application of the decision rules to target detection in real high resolution X-band maritime surveillance radar clutter.
In this paper, a quad-band wearable slot antenna with low specific absorption rate (SAR) is presented. By cutting an inverted V-shaped slot with its arms further extended towards the center of the circular patch, multiple resonant modes of the antenna can be excited to operate on 1.8 GHz DCS, 2.4 GHz WLAN and 3.6/5.5 GHz WiMAX bands. The measured peak gains and impedance bandwidths are about 4.91/7.84/2.58/4.12 dBi and 320/60/80/180 MHz for the 1.8/2.4/3.6/5.5 GHz bands respectively. The SAR of the proposed antenna has been measured using a three layer human tissue model. The estimated SAR values at all the resonant frequencies are well below the threshold limit of 2 W/Kg, which ensures its viability for wearable applications. In order to approximate different parts of the human body, the SAR values have been estimated for three surface sizes, 120 × 120 mm2, 220 × 220 mm2 and 320 × 320 mm2, of the human tissue model, and results are compared. Frequency detuning of the proposed antenna due to bending along x, y and x-y planes has also been carried out and discussed. Further, on arm effect on the antenna performance is investigated, and results are presented. The simulated and measured results are in good agreement, which validates the use of proposed wearable antenna in DCS/WLAN/WiMAX bands.
In order to have the required accuracies in method of moments (MoM) for numerical simulations of ocean scattering at microwave frequencies, we need to account for the much larger wavenumber of sea water relative to that of air. This paper presents simulation results of 2D ocean surface scattering with the required accuracies and that energy conservation is obeyed to 0.01%. A dense grid is required to discretize the MoM dual surface integral equation with up to 240 surface unknowns (120 surface electric field unknowns and 120 surface magnetic field unknowns) per free space wavelength. To solve the matrix equation efficiently, we develop a neighborhood impedance boundary condition (NIBC) technique to solve the matrix equation. We next calculate the emissivities of ocean surfaces using NIBC on surface integral equations using pulse basis/point matching and the Nystrom method. Results are illustrated for L-band and show that emissivities using NIBC combined with Nystrom are accurate to 2×10-4 for vertical polarization and 10-4 for the horizontal polarization. This means that our method can meet the accuracy goal of 0.2 psu salinity retrieval for the NASA Aquarius mission. Results of surface fields and emissivities are also compared to that of impedance boundary condition (IBC) which requires only 10 unknowns per free space wavelength.
GPS is well recognized as the best procedure for outdoor localization. However, it presents limits in indoor localization due to particular geometric difficulties that necessitate specific solution to locate a target inside a building. Also, radio frequency technologies have many disadvantages in indoor localization. Bluetooth and Radio frequency Identification (RFID) are unsuitable for real-time localization because of latency. Ultra-wideband (UWB) localization needs an expensive hardware. Zigbee presents a high interference with wide range of signal frequency because it operates in unlicensed Industrial, Scientific and Medical ISM bands. Light waves also present some limitations due to interferencesfrom fluorescent light and sunlight. The IR based indoor system has expensive system hardware and maintenance cost. To overcome limits and non-availability of radio waves and light waves, an acoustic solution using an array of microphones is presented as a solution for indoor localization, and an optimized deployment is used to improve precision and restrain error. The aim of this work is to propose a 3D indoor audio localization approach inspired by the principle of functioning of the human ear. In order to achieve our goal, we will use a genetic algorithm to obtain the optimized deployment of the used hardware.
In this paper, we deal with a frequency modulated continuous wave (FMCW) radar used for localizing and tracking targets by frequency evaluation of the received radar beat signal. The radar system achieved with a primary radar (reader) and a secondary radar (transponder) is addressed as super high frequency (SHF) radio frequency identification (RFID). Consequently, considering the transponder as an active target, we achieve an identification application thanks to the shift frequency induced by the transponder. Moreover, the impact of the non-linearity behavior of this transponder on the localization performance is investigated, and a solution is proposed for cancelling non-linear effects.
Magnetic field and eddy currents in a cylinder of finite length are calculated by separation of variables. The magnetic field outside the cylinder or inside the bore of the hollow cylinder and shell is expressed in terms of Bessel functions. Both axial and transverse applied fields are considered for the solid and hollow cylinders. The equations for the vector potential components are transformed in one-dimensional equations along the radial coordinate with the consequent integration by the method of variation of parameters. The equation for the scalar electric potential when required is also integrated analytically. Expressions for the magnetic moment and loss are derived. An alternative analytical solution in terms of scalar magnetic potential is derived for the finite length thin shells. All formulas are validated by the comparison with the solutions by finite-element and finite-difference methods.
Study of snow is an important domain of research in hydrology and meteorology. It has been demonstrated that snow physical properties can be retrieved using active microwave sensors. This requires an understanding of the interaction between electromagnetic (EM) waves with natural media. The objective of this work is two-fold: to study numerically all physical forward models concerning the EM wave interaction with snow and to develop an inverse scattering algorithm to estimate snow depth based on radar backscattering measurements at different frequencies and incidence angles. For the first part, the goal is to solve the scattering calculations by means of the well-known electromagnetic simulator Ansoft High Frequency Structure Simulator (HFSS). The numerical simulations include: the effective permittivity of snow, surface scattering phenomena in layered homogeneous media (air-snow-ground) with rough interfaces, and volume scattering phenomena when treating snow as a dense random media. For the second part, the study is extended to develop a retrieval method to estimate snow thickness over ground from backscattering observations at L- and X-band using multiple incidence angles. The return signal from snow over ground is influenced by: surface scattering, volume scattering, and the noise effects of the radar system. So, the backscattering coefficient from the medium is modelled statistically by including a white Gaussian noise into the simulation. This inversion algorithm estimates first the snow density using L-band co-polarized backscattering coefficient at normal incidence and then retrieves the snow depth from X-band co-polarized backscattering coefficients using dual incidence angles.
Metallic pipelines have attendant problems of alternating current (AC) assisted corrosion when installed in the utility corridor with high voltage transmission lines. Research studies in the past and recent years have shown that this corrosion is a primary function of the AC density through the pipe coating defect. While several other AC corrosion risk assessment indices have been proposed, the AC density is regarded as a valuable parameter in assessing pipeline corrosion risk due to AC interference. Also, there exists a threshold value which, if exceeded, guarantees the possibility of pipeline corrosion damage. However, for buried pipelines, monitoring these AC corrosion assessment indices is a major challenge. Therefore, to avoid severe corrosion damage to such pipelines, a corrosion assessment for evaluating the corrosion risk of the pipelines due to AC interference is presented in this paper. The assessment was demonstrated on a buried pipeline in one of the Rand Water sites, South Africa where AC interference is frequent. The overall simulation results yield useful information which may be essential for pipeline operators, most especially Rand Water, South Africa and corrosion engineers for AC corrosion assessment of metallic pipelines installed near transmission lines. The analysis presented in this paper may also be used for the evaluation of a safe position for installing new pipelines near existing power lines right-of-way.
To achieve radial suspension and eliminate the effect of rotor gravity in wind turbines, a novel structure of a generator combined with a magnetic bearing (GCWMB) is proposed in this paper. The GCWMB not only has the characteristics of the traditional permanent magnet (PM) generator but also has the advantages of reducing friction and starting wind speed, eliminating rotor gravity. The structure and principle of the GCWMB are analyzed in this paper. To improve the calculation accuracy of flux density, an analytical model based on the Fourier series decomposition is proposed to establish the model of flux density in the outer air gap. Taking into account the edge effects and the eccentricity of the rotor, an improved equivalent magnetic circuit method is adopted to model and analyze the flux density in the inner air gap. The effectiveness and correctness of the proposed analytical model in the outer and inner air gaps are verified by finite element analysis (FEA) and experiments.
Developed initially for military applications, radar technology is rapidly spreading to areas as diverse as natural resource monitoring, civil infrastructure assessment, and homeland security. Waveform design is a critical component to extract maximum information about the targets or features being probed. Waveforms derived from noiselets, one of the family functions of wavelets, can be advantageous in certain applications owing to their random and uncorrelated properties. In this work, radio frequency (RF) noiselet waveforms are introduced and their performance related to detection of arbitrary target interfaces using the cross-correlation method, a form of matched filtering, is assessed. The application of the RF noiselet waveform for nondestructive testing (NDT) of the multilayered dielectric structures is discussed. The application of wideband noiselet waveforms for multiresolution analysis (MRA) is demonstrated.