Vol. 69

Electromagnetic Interference (EMI) is becoming a crucial issue in the era of modern electronic systems. For EMI measurement, it is required to place a sensor to receive the radiation from the equipment in a suitable test environment. The performance of the sensor depends on its Antenna Factor, which is the ratio of the incident electric field on the antenna surface to the received voltage at the load end across 50Ω resistance. FDTD is one of the efficient numerical techniques to solve radiation and scattering problem in any environments. To the best of the knowledge of the authors no literature is available where FDTD is used to evaluate the Antenna Factor. Here, in this work we applied FDTD to predict the performance of dipole antenna when it is used as a EMI sensor. The results presented here for free space environment are compared with published results.

The scattering behaviour of fractal based metallodielectric structures loaded over metallic targets of different shapes such as flat plate, cylinder and dihedral corner reflector are investigated for both TE and TM polarizations of the incident wave. Out of the various fractal structures studied,square Sierpinski carpet structure is found to give backscattering reduction for an appreciable range of frequencies. The frequency of minimum backscattering depends on the geometry of the structure as well as on the thickness of the substrate. This structure when loaded over a dihedral corner reflector is showing an enhancement in RCS for corner angles other than 90^â—¦.

An effective numerical solution is presented for the plane wave scattering by multilayered periodic arrays of dielectric spheres. The treated structure is a fundamental model of photonic crystals having three-dimensional periodicity. The problem is analyzed by the mode matching method, where the electromagnetic fields in the air and dielectric regions are approximated by using the Floquet harmonics and vector spherical wave functions, respectively. They are matched on the junction surfaces in the least squares sense. Introduction of sequential accumulation in the process of QR decomposition reduces the computation time from O(Q³) to O(Q¹) and the memory requirement from O(Q²) to O(Q¹), with Q being a number of sphere layers. Numerical results are given for CPU time, speed of convergence, and some band gap characteristics.

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.

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.

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.

In this paper, we introduce a new method: support vector regression (SVR) method to modeling low temperature co-fired ceramic (LTCC) multilayer interconnect. SVR bases on structural risk minimization (SRM) principle, which leads to good generalization ability. A LTCC based stripline-to-stripline interconnect used as example to verify the proposed method. Experiment results show that the developed SVR model perform a good predictive ability in analyzing the electrical performance.

Am ultiresolution frequency domain (MRFD) analysis similar to the finite difference frequency domain (FDFD) method is presented. This new method is derived by the application of MoM to frequency domain Maxwell's equations while expanding the fields in terms of biorthogonal scaling functions. The dispersion characteristics of waveguiding structures are analyzed in order to demonstrate the advantages of this proposed MRFD method over the traditional FDFD scheme.

A new technique to evaluate the dielectric constant and loss factor of a homogeneous dielectric material using rectangular shaped perturb cavity has been developed. The values of S-parameters are measured experimentally by placing the sample in the center of the cavity resonator. Sample under test is fabricated in the form of a cylinder. The real and imaginary part of the permittivity can be then calculated from the shift in the resonance frequency and Q-factor. The results of a Teflon sample are also tabulated.

In this paper, a new tapered beamforming function for side lobe reduction in the uniform concentric circular arrays (UCCA)is proposed. This technique is based on tapering the current amplitudes of the rings in the array, where all elements in an individual ring are weighted in amplitude by the same value and the weight values of different rings are determined by a function that has a normalizedgaussian probability density function variation. This novel tapering window is optimized in its parameters to have the lowest possible side lobe level that may reach 43 dB below the main lobe and these optimum weights are found to be function of the number of elements of the innermost ring and the number of rings in the array. The proposed tapering window can be modified to compensate the gain reduction due to tapering when compared with the uniform feeding case.

A general circuit model is proposed for frequency domain analysis of inhomogeneous two-dimensional periodic gratings. Each component of electromagnetic fields is expressed by several spatial harmonic plane waves. Then, two differential equations and two boundary conditions are obtained for the electric and magnetic vectors. Finally a circuit model is introduced for the obtained equations. The circuit model consists of loaded and excited nonuniform coupled transmission lines (CTL).

A generalized equivalent circuit model for waveguide transverse slots is proposed for the efficient analysis of waveguide transitions and waveguide slot antennas and slot-excited antennas. The transverse slots on the broad and end waveguide walls analyzed in this paper are decomposed into three structures: two apertures and an auxiliary waveguide section. The slot aperture in the host waveguide is modeled as an inductance-capacitance-transformer (LCT) combination, for which the equivalent inductance and capacitance are determined by first considering the case of zero-thickness slot, then the transformer turns ratio is calculated for the slot on a finite thickness wall. The effect of the wall thickness is accounted for by a waveguide section having cross-sectional dimensions equal to those of the slot, and length equal to the wall thickness. The loaded slot aperture is modeled along with the external load as a lumped load impedance. Expressions for the inductance, capacitance and transformer turns ratio are obtained in terms of the slot length and width. The obtained expressions facilitate the design of a variety of structures, including waveguide couplers, feeding networks and radiators. The equivalent circuit model proved to be accurate compared to the method of moments solution over a wide frequency band. Comparison of the scattering parameters obtained from the circuit analysis, the method of moments, and the finite-difference time-domain solutions exhibit very good agreement.