There are some limitations on the statement of classic Helmholtz theorem although it has abroad application. Actually, it only applies to simply connected domain with single boundary surface and does not provide any conclusion about the domain where discontinuities of field function exist. However, discontinuity is often encountered in practice, for example, the location of surface sources or interface of two kinds of medium. Meanwhile, most existing versions of Helmholtz theorem are imprecise and imperfect to some extent. This paper not only tries to present a precise statement and rigorous proof on classic Helmholtz theorem with the accuracy of mathematical language and logical strictness, but also generalizes it to the case of multiply connected domain and obtains a generalized Helmholtz theorem in the sense of Lebesgue measure and Lebesgue integral defined on three-dimensional Euclidean space. Meanwhile, our proof and reasoning are more sufficient and perfect. As an important application of the generalized Helmholtz theorem, the concepts of irrotational and solenoidal vector function are emphasized. The generalized Helmholtz theorem and the present conclusion should have important reference value in disciplines including vector analysis such as electromagnetics.

A new algorithm for numerical evaluation of the fields in the near zone of conducting scatterers or antennas of arbitrary shape is developed in the present work. This algorithm is simple, fast, robust andis basedon a preceding calculation of the current flowing on the conducting surface using the electric filed integral equation (EFIE) technique that employs the Rao-Wilton-Glisson (RWG) basis functions. To examine the validity of the near field computational algorithm developed in the present work, it is applied to calculate the near fieldd ue to plane wave incidence on a variety of conducting scatterers. The solution obtainedfor the fields in the near zone is found to satisfy the boundary conditions on both planar and curved scatterer surfaces and the edge condition for structures possessing edges or corners. The solutions obtainedusing the new algorithm are compared with those obtainedusing some commercial packages that employ the finite-difference-time-domain (FDTD). The algorithm defined in the present work gives results which are more accurate in describing the fields near the edges than the results obtained using the FDTD.

In this paper, an efficient algorithm is presented to analyze the electromagnetic scattering by electrically large-scale dielectric objects. The algorithm is based on the multi-region and quasiedge buffer (MR-QEB) iterative scheme and the conjugate gradient (CG) method combined with the fast Fourier transform (FFT). This algorithm is done by dividing the computational domain into small sub-regions and then solving the problem in each sub-region with buffer area using the CG-FFT method. Considering the spurious edge effects, local quasi-edge buffer regions are used to suppress these unwanted effects and ensure the stability. With the aid of the CG-FFT method, the proposed algorithm is very efficient, and can solve very largescale problems which cannot be solved using the conventional CG-FFT method in a personal computer. The accuracy and efficiency of the proposed algorithm are verified by comparing numerical results with analytical Mie-series solutions for dielectric spheres.

This paper presents an effective numerical method for the transient analysis of lossy transmission lines. With the discretization of the spatial variation of voltages and currents along the transmission lines while remaining the temporal derivatives unchanged, a semidiscrete model is derived from the telegrapher's equations. The timestep integration method is utilized to derive the recursive scheme of time advancing. A large time step can be used in the computation, meanwhile, its accuracy is guaranteed. Numerical examples are presented to demonstrate the stability and accuracy of the proposed method.

This work presents a fast computational algorithm that can be used as an alternative to the conventional surface-integral evaluation method included in the electric field integral equation (EFIE) technique when applied to a triangular-patch model for conducting surfaces of arbitrary-shape. Instead of evaluating the integrals by transformation to normalized area coordinates, they are evaluated directly in the Cartesien coordinates by dividing each triangular patch to a finite number of small triangles. In this way, a large number of double integrals is replaced by a smaller number of finite summations, which considerably reduces the time required to get the current distribution on the conducting surface without affecting the accuracy of the results. The proposed method is applied to flat and curved surfaces of different categories including open surfaces possessing edges, closed surfaces enclosing cavities and cavity-backed apertures. The accuracy of the proposed computations is realized in all of the above cases when the obtained results are compared with those obtained using the area coordinates method as well as when compared with some published results.

This paper proposes an approximate space-time-frequency field representation for directive Ultra-wideband antennas useful to be introduced into a system-level evaluation tool. Based on the observation that the very near field collected on a plane close to the antenna exhibits a compact support, such a field is processed in the time domain by the two-dimensional Hermite transform. This approach permits to simultaneously express the antenna impulse response and the transfer function by semi-analytical formulas. The theory is demonstrated by numerical examples which highlights that good representations of complex antennas can be achieved by a small set of associate Hermite functions.

When estimating the electric field level in an indoor environment, the usual complexity of the geometry and its large electric size make it necessary to deal with asymptotic assumptions, also known as high frequency techniques. But, even with these assumptions, the computational complexity, and the CPU-time cost, can be very high. Considering this drawback, this paper proposes the implementation of a "Neural Networks System" for fast calculations of the Electric field in 2D-indoor environments.

Pairing an epsilon-negative (ENG) slab with a munegative (MNG) slab can have some unusual features,suc h as zero reflection and complete tunneling without any phase delay,although each of those two slabs has predicable features. In this paper,the conditions of zero reflection are obtained through an exact analysis, not by the equivalent transmission-line (TL) models. The distributions of fields and Poynting vector outside and inside such paired slabs are analyzed,while evanescent waves also are studied. Simulation results validate the salient features of such paired slabs.

In this work, complex propagation constant of substrate integrated waveguide (SIW) with lossy dielectric is determined with the help of the generalized multipole technique (GMT). We then apply the GMT to compute scattering parameters of some discontinuities in SIW. The obtained results are compared with the results generated by a commercial finite-element solver.

A novel low-pass filter using complementary split ring resonators (CSRRs) for transmission zero control and sharp-rejection is presented. Three different CSRRs resonators cells are etched at the ground plane below a low impedance microstrip line for transmission zero control. A demonstration lowpass filter is designed, fabricated and measured. It agreed with the simulated results well.

The extension of an unconditionally stable precise integration time domain method for the numerical solutions of Maxwell's equations to circular cylindrical coordinate system is presented in this paper. In contrast with the conventional cylindrical finite-difference time-domain method, not only can it remove the Courant stability condition constraint, but also make the numerical dispersion independent of the time-step size. Moreover, the first-order absorbing boundary condition can be introduced into the proposed method successfully, whereas the alternating-direction-implicit finitedifference time-domain method may become instable for open region radiation problems terminated with absorbing boundary conditions. Theoretical proof of the unconditional stability is mentioned and the numerical results are presented to demonstrate the effectiveness of the proposed method in solving electromagnetic-field problem.

The eigenwave dispersion (its initial periodicity-dispersion component) and the H0i-wave power flows (via the partial wave concept proven) are examined in a periodic iris-loaded circular waveguide (PICW). The eigen-values and modes are classified; arbitrariness of a Bragg wave-point location, the eigenwave interpretation, the contradirectional power flows, the asymmetric wave hybridity, and etc., are found and/or explained. All of the results are valid to the class of periodic-boundary structures (PBS).

The new definition of arbitrary isolation between antennas is proposed according to the microwave network theory. The multilevel fast multipole algorithm (MLFMA) with the near-field preconditioner is implemented to predict the isolation between multiple antennas on electrically large platforms over a wide frequency range. Experimental results show that the isolation defined in this paper is more practical than the traditional one. Finally the radiation pattern and the isolation results for the ultra-shortwave antennas mounted on full-scale models such as an aircraft and a ship are obtained and discussed, which can give significant instructions to the platform-mounted antennas design.

The paper presents a new algorithm for a 2-dimensionnal direction of arrival estimation. Based on the extended Kalman filter (EKF), we analyse a recursive procedure for 2-dimensional directions of arrival (DOA) estimation and we will employ the two-L-shape arrays. A new space-variable model which we call a spatial state equation is presented using array element locations and incident angles. In this paper we briefly recapitulate the most important features of the extended Kalman filter (EKF). The performance of the proposed approach is examined by a simulation study with three signals model. The simulation results show a good estimate performance.

Simple and accurate models based on artificial neural networks (ANNs) are presented to accurately determine the physical dimensions of coplanar strip lines (CPSs). Five learning algorithms, Levenberg-Marquardt (LM), bayesian regularization (BR), quasi- Newton (QN), conjugate gradient with Fletcher (CGF), and scaled conjugate gradient (SCG), are used to train the neural models. The neural results are compared with the results of the quasi-static analysis and the synthesis formulas available in the literature. The accuracy of the neural model trained by LM algorithm is found to be better than 0.24% for 10614 CPS samples.

Akind of controllable metamaterial absorbing structure is presented in this paper, both transmission coefficient and single radar cross section (RCS) are electrically controlled. This structure is composed from split ring resonators (SRRs) and metallic wire arrays including pin diodes, pin diodes are periodically inserted at these wire arrays discontinuous, and they can be either in an on state or in an off state depending on the voltage to realize the electronic control. We use the metallic wave-guides theory, ANSOFT HFSS, high impedance surface (HIS), radiation boundary conditions, and a master-slave (M/S) relationship between each of the periodic boundary conditions (PBC's) pairs, to simulate the transmission coefficient and single radar cross section (RCS), and simulation proves that this method and technology can absorb vertical incident microwave. This is very useful for getting zero-reflected power and better aircraft stealth performance in the future.

The high power generation and transmission for TM modes in a parallel-plate waveguide filled with three-layered medium called sandwich structure are investigated. The transmission power could never exceed the input power of the source in a conventional parallel-plate waveguide filled with homogeneous or inhomogeneous right-handed material (RHM) or homogenous left-handed material (LHM). Based on the stratified medium theory, extremely high power can be generated and transmitted if the waveguide is composed of RHM-LHM-RHM or LHM-RHM-LHM sandwich structure with the medium parameters and layer thickness being properly chosen. Different from the TE case, the dominant mode exists in such a structure is TM₀ mode which can be always supported despite the size of the waveguide. From our numerical results, we find that the high power generation and transmission can be easily realized even in the more realistic case where the LHM is described by the Lorentz medium model.

A compact open-loop resonator bandpass filter with suppression of the second and the third harmonics is demonstrated in this paper. This novel filter is based on a Tri-Section SIR to achieve size minimization and suppressed spurious response. The simulations and measurements of a 0.9 GHz prototype bandpass filter are presented. The measured results agree well with simulation and calculation.

Approximate, non-singular kernels are often used in moment-method formulations coping with thin-wire structures. Their use has important consequences, one of which is the appearance of oscillations in the computed currents when the number of sub-domain basis functions is sufficiently large. These oscillations are not due to round-off errors. In this paper, a smoothing procedure is used in conjunction with Galerkin's formulation with piecewise sinusoidal functions, which yields non-oscillating current distributions. Special attention is paid to the solutions over a wide range of discretization levels (number of basis/testing functions), in order to examine and illustrate the similarities and differences between results obtained with and without the proposed remedy. Finally, a comparison with results derived with the exact kernel is provided.

This paper starts with the characteristics and advantages of microwaves processing. The shortcomings of fixed frequency, typically at 2.45 GHz were also mentioned. On account of this, a newly developed variable frequency microwave (VFM) fabrication was mentioned and adopted in place of the fixed frequency process. Two cases of fixed frequency microwave processing of materials were described; the characteristics, pros and cons of each case was mentioned and commented. Two cases of processing materials using variable frequency microwave facility (VFMF) were mentioned; the advantages and limitations of each case were discussed. The microwave processing of materials provides improved mechanical, physical and electrical properties with much reduced processing time. Furthermore, variable frequency microwave processing is more superior to its fixed frequency counterpart except that the cost of the facilities of the former is much higher than the latter at this point in time but it appears that the price will drop in the coming ten years.