We develop a new adaptive inversion procedure: Data-adaptive Resolution Inversion (DRI) method, which eliminates the need of selecting a parameterization prior to inversion. Instead, one performs a hierarchical search for the correct parameterization while solving a sequence of inverse problems with an increasing dimension of parameterization. A parsimonious approach to inverse problems usually involves the application of the same refinement consistently over the complete spatial domain. Such an approach may lead to over-parameterization, subsequently, to unrealistic conductivity estimates and excessive computational work. With DRI, the new parameterization at an arbitrary stage of inversion sequence is allocated such that new degrees of freedom are not necessarily introduced all over the spatial domain of the problem. The aim is to allocate new degrees of freedom only where it is warranted by the available data. Inversion results confirm that DRI is robust and efficient for multiparameter inversion of multicomponent borehole electromagnetic measurements.

Short-wavelength radar networks are expected to complement current long-range weather radar systems. Accordingly, we proposed a configuration for such a network constituting pulse compression radars in order to use frequency resources efficiently and obtain multi-static information. We developed high resolution Ka-band pulse compression weather radar system as a test-bed. Using a commercial direct digital synthesizer (DDS) and field programmable gate array (FPGA) control, we generated linear and arbitrary nonlinear frequency modulated waveforms for low range sidelobes. Further, we completed a high duty factor system with a solid-state power amplifier. In a vertical-pointing mode, we were able to employ the developed radar to detect moderate rainfall up to 15 km. Details of the system design, hardware structure, data acquisition and processing algorithms were described. To validate the performance of the proposed radar system, we conducted several experiments by measuring cloud, snow and rain.

We numerically investigate the interaction of nonlinear pulses in coupled transmission lines with regularly spaced Schottky varactors. The c mode and π mode are two different propagation modes that can be developed on a coupled line. Recently, we have found that both modes can support soliton-like pulses due to the presence of the Schottky varactors and proposed a method of doubling repetition rate of the incident pulse stream. Through numerical evaluations, we find that small c-mode pulses are generated by colliding two π-mode pulses traveling in the opposite directions. Utilizing this unique property, the repetition rate of incident pulse stream can be increased by the factor greater than 2.

In this paper, single-crystalline silver filaments with periodic, pearl-chain-like structures are fabricated by electrodeposition without using any templates, surfactants, and additives. Simulations demonstrate that excited surface waves may sustain on silver pearl chains in middle infrared (Mid-IR) range. Based on the propagation features of surface waves on the silver filaments, this structure can be applied for electromagnetic wave transmittance in Mid-IR range. The propagation features of surface waves on the silver filaments indicate the structure application for Mid-IR wave transmittance.

A miniaturized internal wideband antenna suitable for integration with the printed circuit board (PCB) of a wireless universal serial bus (WUSB) dongle is presented in this paper. The proposed antenna mainly consists of a folded metal plate with two sides beveled. By introducing a short-circuited pin connected to the system ground and etching a pair of slots in the bevel sides of the folded metal plate, a large impedance bandwidth from 2.4 GHz to more than 11 GHz is obtained, which easily covers the 2.4 GHz WLAN, WiMAX, S-DMB and UWB frequency bands. The effects of the short-circuited pin and the narrow slots on the impedance matching of the proposed antenna are investigated. The proposed antenna is easy to be fabricated by bending a sample metal plate due to its miniaturized geometry of 5×12×12.5 mm³. Details of the antenna design are described, and experimental results of the constructed prototypes are presented and discussed.

A new model (EWGM) is presented to predict the resonant frequency of Rectangular Dielectric Resonator Antenna (RDRA) more accurately. Correction factors are introduced to calculate the effective dimensions by considering the effect of relative permittivity and aspect ratios (length/height and width/height) of RDRA. Results obtained from EWGM are compared with previous studies and experimental data to show its accuracy and effectiveness.

A fractal array is an antenna array which holds a property called "self-similarity". This means that parts of the whole structure are similar to the whole. A recursive procedure for evaluating the impedance matrix is allowed primarily by exploiting the self-similarity. However, numerous fractal arrays are extremely complicated in structure. Therefore, for these arrays, it is extremely elaborate to formulate explicitly a recursive relation. This paper proposes a simple procedure for evaluating, without formulating explicitly a recursive relation, the impedance matrix of fractal and fractile arrays; a fractile array is any array with a fractal boundary contour that tiles the plane without gaps or overlaps.

Non Destructive Testing techniques are more and more exploited in order to quickly and cheaply recognize flaws into the inspected materials, specially for carbon fiber reinforced polymers in recent years. Their production which are widely used both in civil and military applications, is an elaborate process un-free from faults and problems. Problems during the manufacturing, such as plies' overlapping, can cause flaws in the resulting material, this way compromising its integrity. Within this framework, this work aims to propose a design of ferrite core probe for eddy current non destructive evaluation, in order to investigate the presence of defects in carbon fiber epoxy composite materials. In this context, modelling is a powerful tool for inspection improvements. It helps probe-coil designers to optimize sensors for each examination requirement, providing better understanding of the involved physics, supporting operator training and increasing defect analysis reliability. Particularly, Finite Element based analyzes will be carried out into this path. After this step, in order to improve the quality of simulated measurement, a filtering technique has been exploited in order to improve the accuracy and performance of the flaw detection.

We have derived a one-variable metric function for fast and accurate complex permittivity extraction of low-to-high-loss materials using reflection-only microwave non-resonant measurements at one frequency. The metric function can be modified to facilitate fast computation of the complex permittivity of materials for various applications (e.g., relative complex permittivity measurement of low-loss materials). It is useful as a measurement tool for broadband measurements of complex permittivity of samples with substantiate lengths. In addition, the method is applicable for measurement of complex permittivity of dispersive materials or complex permittivity of non-dispersive samples in limited frequency-band applications, since it is based on point-by-point (or frequency-byfrequency) extraction. It is validated by a numerical analysis and measurements of a liquid sample.

The nonlinear responses of a one-dimensional heterostructure containing two kinds of single-negative materials with an air gap are investigated. It is shown that the frequency of zero-phase gap bistable heterostructure can be tuned simply by adjusting the width of air gap. On the other hand, the optical bistability is achieved at very low values of input intensity due to the enhancement of Kerr nonlinearity near the frequency of the defect mode. It is shown that transmission of the structure is relatively insensitive to incident angle and losses.

A novel dual-wideband printed monopole antenna is proposed for wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications. The proposed antenna consists of a T-shaped monopole on top and dual combined G-shaped slots located symmetrically on the ground plane to achieve a dual-wideband performance. Prototype of the proposed antenna has been constructed and tested. The measured 10 dB bandwidths for return loss are 1.76 GHz from 2.13 to 3.89 GHz and 0.92 GHz from 5.03 to 5.95 GHz, covering all the 2.4/5.2/5.8 GHz WLAN and 2.5/3.5/5.5 GHz WiMAX bands. And this antenna also has omni-directional patterns over the lower operating range.

Reconstructing high-accuracy Digital Elevation Model (DEM) is influenced by phase errors, such as phase trend, low coherence problems and phase unwrapping. These problems could result in the conversion errors from the phase to height. In this paper, a method is proposed to reconstruct the high-accuracy DEM using satellite interferometric synthetic aperture radar (InSAR). The proposed algorithm mainly aims to reduce the phase errors from the phase trend and low coherence problems. It consists of three steps. Firstly, the orbit state vectors are precisely interpolated in 3-D coordinates rather than in a separate dimension with the exploration of the orbital elements. Secondly, the relationship between external DEM and the interfermetric phase is built by the improved precise geo-location algorithm. The phase trend is estimated according to the topographic information and then removed from the unwrapped interferogram. Thirdly, the interferogram in low coherent regions are all updated with the simulated phases from actual DEM. The accuracy of the InSAR derived DEM can be significantly improved without any ground control points (GCPs), especially in those regions contaminated by masses of residues. Meanwhile, the phase trend caused by atmosphere effects or orbits uncertainty can also be eliminated by using this method. The experiment has demonstrated the proposed method can yield quite satisfactory results for producing high-accuracy DEM using Envisat data.

A radiofrequency field (RF) field exists inside body tissue during magnetic resonance imaging (MRI). If any implanted medical device is present, there can be a very intense concentration of the scattered RF field in the tissue surrounding certain parts of the implant. This causes tissue heating that can reach dangerous levels. Scattered field considerations show that it is possible to neglect the loading effect of the implant on the MR RF source. This leads to an incident field simplification. The presence of the implant in nonhomogeneous tissue increases the complexity of the scattering problem. An approach is presented that makes the computational problem considerably smaller. A method of moments (MoM) formulation of the electromagnetic model is presented. The relevant issues that arise during a finite element method (FEM) formulation are also discussed. The methods are illustrated by solving the problem for a typical implant using MoM as well as FEM.

Miniaturized ferrite ring patch antennas (RPAs) were designed and fabricated for multiple-input multiple-out (MIMO) applications. Design parameters of higher-order mode ferrite RPAs, 1-RPA and 2-RPA, were optimized, and antenna performance of the ferrite 1-RPA was evaluated. The Z-type hexaferrite and 2%-weight borosilicate glass composite was used for the ferrite antenna disk. The measured permeability (μ_r) and permittivity (ε_r) of the hexaferrite were 2.59 and 5.7, respectively, at 2.5 GHz. Threemode orthogonal radiation of the ferrite 1-RPA was experimentally confirmed. With regard to the ferrite 2-RPA, excellent isolation (-40 dB) between ports 1 and 2 was achieved at 2.5 GHz. This excellent isolation property is attributed to both mode 3 orthogonal radiations of the bottom and top RPAs. The volumes of the 1- and 2-RPA were reduced to 14.5% and 34.5%, respectively, from 95 cm3 of a dielectric 2-circular patch antenna (2-CPA) volume.

Analytic expressions for the nonlinear absorption coefficient (nonlinear absorption coefficient=NAC) of a strong electromagnetic wave (laser radiation) caused by confined electrons for the case of electron-optical phonon scattering in doping superlattices (doping superlattices=DSLs) are calculated by using the quantum kinetic equation for electrons. The problem is also considered for both the absence and the presence of an external magnetic field. The dependence of the NAC on the intensity E₀ and the energy hΩ of the external strong electromagnetic wave (electromagnetic wave=EMW), the temperature T of the system, the doping concentration n_D and the cyclotron frequency Ω_B for case of an external magnetic field is obtained. Two cases for the absorption: Close to the absorption threshold ∣khΩ-hω₀∣≤ε and far away from the absorption threshold ∣khΩ-hω₀∣≥ε (k=0, ±1, ±2..., hω₀ and ε are the frequency of optical phonon and the average energy of electrons, respectively) are considered. The analytic expressions are numerically evaluated, plotted, and discussed for a specific DSLs n-GaAs/p-GaAs. The computations show that the NAC in DSLs in case presence of an external magnetic field is much more greater than to it is absence of an external magnetic field. The appearance of an external magnetic field causes surprising changes in the nonlinear absorption. All the results for the presence of an external magnetic field are compared with those for the absence of an external magnetic field to show the difference.

Because the nearspace slow-moving platform borne synthetic aperture radar (SAR) can realize high resolution imaging using low pulse repetition frequency (PRF), a full-aperture ScanSAR (FA-ScanSAR) operation, which switches the range beam pulse by pulse, was proposed for wide swath imaging. This operation separates the wide swath into several sub-swaths, and each of which can be illuminated by a narrow range beam. The SAR antenna switches the range beam to point at each of the sub-swaths in turn, transmits pulses and receives echoes pulse by pulse. The design method of main system parameters and the calculating expressions of the performance indexes are addressed in the paper. A design example is given to compare the performance of the conventional strip operation, ScanSAR and FA-ScanSAR operation. The results show that FA-ScanSAR operation can obtain high resolution by full aperture accumulation in wide swath and improve the signal-to-noise ratio of SAR images for the nearspace slow-moving platform borne SAR.

This paper deals with the development of the Wiener-Hopf method for solving the diffraction of waves at fine strip-slotted structures. The classical problem for diffraction of plane wave at a strip is an important canonical problem. The boundary value problem is consecutively solved by a reduction to a system of singular boundary integral equations, and then to a system of Fredholm integral equations of the second kind, which effiectively is solved by one of three presented methods: A reduction to a system of the linear algebraic equations with the help of the etalon integral and the saddle point method numerical discretization based on Gauss quadrature formulas the method of successive approximations. The solution to the problem in the first method contains a denominator that takes into account the resonance process. Moreover, the precision of the main contribution of the short-wave asymptotic solution is ensured down to the quasi-stationary limit. The paper presents also comparisons of with earlier known results.

In this paper, we propose a brief and general process to compute the eigenvalue of arbitrary waveguides using meshless method based on radial basis functions (MLM-RBF) interpolation. The main idea is that RBF basis functions are used in a point matching method to solve the Helmholtz equation only in Cartesian system. Two kinds of boundary conditions of waveguide problems are also anlyzed. To verify the e±ciency and accuracy of the present method, three typical waveguide problems are analyzed. It is found that the results of various waveguides can be accurately determined by MLM-RBF.

We propose a planar focusing antenna design, which has the same performance as its parabolic counterparts and can be realized using PEC-backed gradient index dielectrics. In this design, quasi-conformal transformation optics is first utilized to transform a parabolic surface into a planar one, then the anisotropy factor of the resultant material is minimized, and the material is approximately treated as isotropic. Examples with realizable material parameters are given, and the simulation results validate the design. The proposed method could be used to design planar focusing antennas with high directivity and similar devices. The idea can also be applied to new device designs in optics engineering.

The absorption and dispersion properties of a Kobrak-Rice 5-level quantum system are investigated. It is shown that the dressed states of such a system are phase-dependent. It is also demonstrated that the absorption, dispersion and group index can be controlled by either the intensity or relative phase of driving fields. Moreover, we have shown that by applying an incoherent pumping field the absorption doublet switches to gain doublet, and the absorption free superluminal light propagation appears which can be used in the transfer of information process.