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.

In this paper, an ultra-wideband (UWB) bandpass filter (BPF) with a notch-band at 5.8 GHz is presented. The proposed filter is constructed with multiple-mode resonator (MMR) using novel dumbbell stubs and one-arm-folded interdigital coupled lines in the input and output sides. The MMR consists of three pairs of shunt dumbbell stubs and a high impedance microstrip line. By adjusting the dimensions of the dumbbell stubs, the resonant modes of MMR are allocated in the UWB band. The arm-folded interdigital coupled lines are used to obtain a notch-band at 5.8 GHz. Finally, the proposed UWB BPF is fabricated. The simulated and measured results are in good agreement with each other.

A Coplanar Wave guide (CPW) fed printed monopole antenna with reduced radiation hazard from a mobile handset is presented. The printed metal stripes in the back side of the monopole modify the far field pattern ideal for mobile handset. The antenna offers a bandwidth of 200 MHz when printed on a substrate of dielectric constant (εr) 4.4 and thickness 1.6 mm with an overall dimension of 42x31.7 mm². Experimental and simulation studies of the antenna radiation characteristics of the proposed antenna are presented and discussed. A 20 dB reduction of radiated power in one quadrant of the radiation pattern offers a reduction of radiation towards the users head.

In this paper, a new method for calculating transient electromagnetic responses of AC/DC power system with external electromagnetic pulse interference is proposed. An input-output model of three-phase bridge rectifier is presented for the transient calculation. In order to study the effect of the external electromagnetic pulse on the system, the field-to-line coupling model is introduced, and finite-difference time-domain method is adopted. Thus, the modeling method utilizes the analysis methods of the electric circuits and electromagnetic fields synthetically to deal with the coupled field-circuit problems. The model and algorithm are validated by comparing the calculation results with the experiment ones. Finally, the effects of some circuit parameters on transient responses are discussed. The method proposed in this paper lays the foundation for further researches on the transient electromagnetic performance of independent electrical power systems containing power electronics.

We derive integral representations suitable for studying the focusing of electromagnetic waves through a symmetrically hyperbolic focusing lens into uniaxial crystal in the presence of cylindrical and coma aberrations using Maslov's method. The uniaxial crystal used is the negative crystal LiNbO₃. Numerical computations are made to obtain the results for focused fields inside negative uniaxial crystal with several different orientations of the optical axis in the plane of incidence. The effects of aberrations inside uniaxial crystal and isotropic medium are also noted. The results are compared with those obtained by Kirchhoff-Huygens integral and Maslov's method which are in good agreement.

In this work, based on the principle of the electromagnetic reflection and transmission, we first present a theoretical analysis of a super-resolving lens with anti-reflection and phase control coatings (ARPC). This ARPC is capable of reducing the reflectivity of superlens surface and making phase difference approaching zero. The principle of ARPC is discussed in detail and the engineer condition for super-resolution imaging is obtained and the best range of the permittivity of ARPC coatings is obtained. The results demonstrate that the subwavelength resolution of our lens with ARPC has been enhanced. Such remarkable imaging capability using ARPC promises new potential for nanoscale imaging and lithography.

This paper describes the design and analysis of a Microstrip Reflectarray Antenna (MRA) with Minkowski shape radiating element at frequency of 11 GHz. This structure has been analyzed and compared with the traditional reflectarray element (square element patch). It is found that this antenna array has lower sidelobe level (SLL) characteristic which is down to -25 dB. This MRA has maximum realized gain of 29.6 dB with half-power beamwidth (HPBW) of 3.7°. The validation for the proposed MRA is done by comparing the simulated and measured E-plane radiation pattern. The difference margin between sweeping realized gain (simulation) and sweeping power received (measurement) had been compared within the frequency range of 10--12 GHz. A very good agreement is found from the comparison between simulation and measurement.

An efficient hybrid method is presented to obtain the current distribution of both non-uniformly linear and planar arrays By sampling the array factor of a desired radiation pattern, the proposed method provide Fourier coefficients and uses the Least Mean Square method (LMS) to solve the system of equations in order to obtain current distribution in associate with the desired radiation pattern. Obtained side lobe level is 3 dB lower than conventional methods such as LMS method or Legendre function method.

In this paper, we present a procedure to calculate the discrete modes propagated with Crank-Nicolson FDTD in metallic waveguides. This procedure enables the correct excitation of this kind of waveguides at any resolution. The problem is reduced to solving an eigenvalue equation, which is performed, both in a closed form, for the usual rectangular waveguide, and numerically in the most general case, validated here with a ridged rectangular waveguide.

A novel and simple antenna applicable to active RFID tags is designed. The designed antenna has been skillfully integrated with the active RFID tag circuit. The antenna consists of two parts. One part comprises stacked shorted patches and a ground plane. The other one is an active tag circuit mounted on the bottom of the antenna. By using the offset shorting posts technique, the proposed antenna can achieve an enhanced operating bandwidth with a small size. The measurement results reveal that the antenna has return loss less than -10 dB within the bandwidth of 42 MHz (from 914 MHz to 956 MHz), which totally covers the 5MHz bandwidth from 920MHz to 925 MHz (The band is also allowed for passive RFID) requirement for active RFID in China.

Antenna arrays with shaped power patterns have many applications in communications and radars. Many antenna array synthesis techniques for shaped patterns have been developed in the past years, and most of them deal only with uniformly spaced arrays. In this paper, a new method is proposed for the synthesis of nonuniform linear antenna arrays with shaped power patterns. The proposed synthesis method consists of three steps. First, we find a satisfactory power pattern for the required radiation characteristics by solving a constrained least-squares problem which is obtained with the help of non-redundant representation of squared magnitude of a linear array factor. Then, we factorize the polynomial associated with the power pattern by using polynomial rooting, and consequently obtain the corresponding field patterns. Finally, the forward-backward matrix pencil method is used to obtain a nonuniform linear array with optimized excitation magnitudes, phases and locations for a specific choice of field patterns. The synthesized array has a smaller number of elements than the one with uniformly spaced elements for the same pattern performance. Several synthesis experiments are conducted to validate the effectiveness and advantages of the proposed synthesis method.

Accurate approximations of the conductance and the conductance bandwidth of an electrically small antenna valid in resonant and antiresonant ranges were found. It is shown that the conductance bandwidth of an efficient antenna tuned on maximal power of radiation is inversely proportional to the magnitude of the frequency derivative of the input impedance |Z'(ω_cd)| of the antenna at frequency of maximal conductance. That is a generalization of the well known relationship according to which, the conductance bandwidth of an antenna tuned on resonance in resonant ranges is inversely proportional to the magnitude of the frequency derivative of the input reactance of the antenna |X'₀(ω₀)| at resonant frequency. Obtained approximate formulas display inverse proportionality of the conductance bandwidth to the approximate quality factor of the antenna throughout resonant and antiresonant ranges. A differential definition of the fractional conductance bandwidth was formulated, which is convenient for the case of closely spaced resonances of an antenna. As an example, numerical calculations for oblate spheroidal and spherical antennas in shells with negative permittivity in resonant and antiresonant ranges was used to confirm accuracy of the obtained approximations of the conductance and the conductance bandwidth of an electrically small antenna.