This paper discusses the application of computational electromagnetics (CEM) for electromagnetic compatibility (EMC) problems of integrated circuits (ICs). It is known that the application of CEM is versatile in solving a wide range of problems. This paper focuses on the electromagnetic study of quad flat non-lead (QFN) packaged ICs, one monolithic microwave integrated circuit (MMIC) and another radio frequency integrated circuit (RFIC), from the individual chip to system in package (SiP). Full-wave electromagnetic technique is conducted in the modelling and simulation. Both chips are found producing radiated emissions in horizontal directions as omnidirectional antennas at working frequencies and then directional at resonance frequencies.
Because the oversized, ultra short-range and arbitrary-shape goals cannot be imaged by Fourier transform algorithm, a Boundary Element Method(BEM) is presented for short-range millimeter wave holographic imaging.Through the discrete boundary integral equation, the discrete electromagnetic fields on the source surface and holographic surface are obtained. They are linked by a transfer matrix. Finally, the discrete electromagnetic fields obtain target holographic image. Due to the complexity of the transfer matrix, the Distributed Source Boundary Point Method (DSBPM) is introduced to calculate it, which greatly simplifies the calculation process. The simulation experiments of three-dimensional hemisphere imaging show the sensitivity of the imaging algorithm to test error, and regularization method has been proposed. The actual measurement of the four small metal balls verifies the validity of the imaging algorithm for large target imaging. The imaging results show that holographic imaging of the boundary element method can obtain high resolution and high amplitude accuracy.
In most practical applications of the phased array antennas, the generated nulls toward the interfering signals should have enough depth and width to accommodate fluctuations in frequency and direction of the interferer. Due to these fluctuations, the nulls can be easily deviated from its desired angular locations in the traditional adaptive nulling arrays since the nulls are very sharp and sensitive. An innovative technique for wide nulling arrays has been recently presented. The wide nulls can be introduced by setting properly the excitation coefficients of the two edge elements of the antenna array. In this paper, the effect of frequency fluctuation on the nulling performance is investigated. By generating wide and deep nulls toward and around the interference directions, the proposed method provides robustness against frequency fluctuation. Simulation results in realistic situations with frequency fluctuation are presented to illustrate the performance of the proposed technique. Comparisons with the standard fully adaptive nulling array are shown.
Two dimensional (2D) radar coincidence imaging is an instantaneous imaging technique which can obtain 2D focused high-resolution images using a single pulse without the limitation to the target relative motions. This paper extends the imaging method to three dimensions. Such a three-dimensional (3D) radar imaging technique does not rely on Doppler frequency for resolution and has an extremely short imaging time (shorter than a pulse width), resulting in two remarkable properties: 1) it does not require the relative rotation between targets and radar; 2) it can considerably avoid the image blurring in processing noncooperative targets without motion compensation. 3D radar coincidence imaging consequently can derive high-quality images for either the targets that are stationary with respect to radars or the ones in maneuvering 3D rotations. The validity of the proposed imaging technique is confirmed by numerical simulations.
In this paper, the integrated formulas for the electromagnetic field in the planar boundary between isotropic and onedimensionally anisotropic media due to a horizontal electric dipole situated on the interface are treated in detail, and the calculable field components are given in terms of series that involve confluent hypergeometric functions, namely, the Fresnel and exponential integrals, and the expressions are more complex than the isotropic case. The exact expressions and simplified formulas can be easily reduced to the corresponding isotropic case. The results are useful to study the propagation of the electromagnetic waves on the boundary of one-dimensionally anisotropic earth or sediments.
A planar inverted F antenna is combined with passive (reactively loaded) elements in order to implement a multi-frequency configuration appropriate for biomedical applications in microwave frequencies. A case study of an electronically Reconfigurable PIFA (R-PIFA) is pursued for the detection of temperature abnormalities in human tissue phantom using microwave radiometry, where the performance of the structure is optimized with respect to input impedance matching in multiple frequencies. The optimization of the array is performed using a Genetic Algorithm (GA) tool as a method of choice. Due to its limited physical size, the proposed R-PIFA can also be used as a portable antenna system for deployment in mobile medical applications.
In a time domain Marching-on-in-degree (MOD) solver based on a Galerkin implementation of the Method of Moments (MoM), it is observed that the matrix elements for the matrix to be inverted contain integrals that are similar to the ones encountered in a frequency domain MoM solver using the piecewise triangular patch basis functions. It is also observed that the error in the evaluation of the matrix elements involving these integrals are larger in the time domain than those involved in the frequency domain MoM solvers. The objective of this paper is to explain this dichotomy and how to improve upon them when using the triangular patch basis functions for both the time and the frequency domain techniques. When the distance between the two triangular patches involved in the evaluation of the matrix elements, are close to each other or when the degree of the Laguerre polynomial in a MOD method is high, the integral accuracy will be compromised and the number of sampling points to evaluate the integrals need to be increased. Numerical results are presented to illustrate this point.
The frequency dependent characteristics of grounding system buried in half homogenous earth model have been discussed before; however, the importance of mutual inductive and capacitive effects on the grounding problems in both frequency and time domains is unclear. In order to study the importance of the mutual inductive, capacitative and conductive effects on the grounding problem in both frequency and time domains, hybrid method, which is a hybrid of Galerkin's method of moment and conventional nodal analysis method, has been used to study the dominant factor among the mutual inductive, capacitive and conductive effects in the paper.
In this paper the derivation of a rigorous expression of the input admittance of a coaxially fed, infinite, lossy parallel plate waveguide (PPWG) is presented. The derivation makes use of the dyadic Green's function of the PPWG expressed as series a cylindrical wave-functions. Losses into the dielectric plates and on the conductors are considered rigorously. The approximation used in results presented in the past literature are critically discussed. Numerical experiments are performed to show the effects of the finite conductivity on the input impedance of the PPWG.
A finite element method based on the first order system LL* (FOSLL*) approach is derived for time harmonic Maxwell's equations in three dimensional domains. The finite element solution is a potential for the original field in a sense that the original field U is given by U = L*u. The Maxwellian boundary data appears as natural boundary condition. Homogeneous Dirichlet boundary conditions for the potential must be imposed, and they are circumvented with weak enforcement of boundary conditions and it is proved that the sesquilinear form of the finite element system is elliptic in the space where the Dirichlet boundary conditions are satisfied weakly.
A hybrid approach to find the optical response of periodic photonic structures to incident light is presented. The approach is based on a scattering matrix combination of the Finite Element Method (FEM) and the Fourier Modal Method (FMM). Optical response calculations include: scattering in both reflection and transmission directions, absorption and electric and magnetic field distributions inside the structure. The approach is tested on a structure --- composed of dielectric and metallic materials --- that is periodic in one direction. An analysis of the calculation accuracy shows that the approach depends on the subdivision into FEM and FMM domains and that the optimal subdivision depends on the calculations frequency range as well as on the structure geometry. For testing, we use the commercial FEM solver contained in CST Microwave Studio and a based on C/C++ Fourier Modal Method implementation.
In this paper, general solution for the electric and magnetic fields are developed using the vector potentials A and F when the wave is propagating in fractional dimensional space. Different field configurations can be analyzed using the developed expressions for electric and magnetic fields, here we have analyzed TEz and TMz modes when the wave propagates in fractional space inside a rectangular waveguide. It is observed that wave propagation behavior in fractional space changes substantially from the non-fractional space. It is also observed that the obtained results show generalization of the concept of solutions for wave propagation from integer to fractional space. As a special case, when all the dimensions are considered integer, then all classical results are recovered.
This paper presents the design of a monolithic structure with dual-band quasi-elliptic frequency selective filtering responses. The frequency selective structure consists of a two-dimensional (2-D) array of cavities apertured with six ring slots. The transmission response is with a quasi-elliptic passband in lower frequency, and an elliptic passband in upper frequency. By placing transmission zeros near the passband edge, the proposed structure is characterized with high selectivity, rapid rolloff, and high separation between two passbands. Besides, the working principles and influence of the dimensional parameters are fully investigated with simulations and analysis, which is helpful to the design. In this design, five resonances and three transmission zeros are obtained with a simple unit by introducing coupling and phase controlling. This work will be meaningful in study of three dimensional frequency selective structures with high performance.
Planar antenna array design is one of the most important electromagnetic optimization problems of current interest. This paper introduces a recently developed metaheuristic algorithm, known as the Invasive Weed Optimization(IWO), to the pattern synthesis of planar antenna arrays with desired pattern nulls and sidelobe level by amplitude-only and position-only optimization. The steps in the problem formulation are presented along with a design example that illustrates the performance of the IWO algorithm. Three examples have been presented and solved. Simulation results are proposed to compare with published ones to verify the effectiveness of the IWO algorithm for planar arrays.
The authors recently presented a novel microwave tomography method for creating quantitative images of the electromagnetic properties of the interior of unknown objects . This method is based on a time-domain inverse solver which uses the multi-illumination technique and includes the dispersive and heterogeneous characteristic of the object. The Frequency Dependent Finite Difference Time Domain ((FD)2TD) and Genetic Algorithm (GA) technique were utilized for determining unknown characteristics of the object. In the present paper, the calibration of measured data are described and image reconstruction results for preliminary experiments performed at the University of Manitoba's Microwave Tomography Laboratory and at the Institut Frsenel are presented.
In this paper, the comparison of the performances of planar broadband dipole antenna, broadband folded dipole antenna and broadband bent dipole antenna in broadband scenario is presented. All the three antennas have been designed, developed and evaluated for their electrical characteristics such as VSWR, radiation patterns and gain in the frequency range of 100-1000 MHz. Simulated and measured results are presented.
Radar echo of ballistic midcourse target contains unique motion information of the target, which can provide important evidence for target recognition. A wideband radar echo simulation model for midcourse precesional target is developed, where the micro-motion model, electromagnetic scattering calculation and linear frequency modulated (LFM) radar signal model are integrated. Firstly, the position variation of each scattering center of the moving target is analyzed. Then, the high frequency method is used to judge the masking effect of scattering centers of the rotational symmetry target. Finally, the wideband radar echo is simulated, and the impacts of high speed translational motion, non-precession movement and non-idealization of the scattering centers on the echo are also analyzed.
A low radar cross section (RCS) metamaterial absorber (MMA) with an enhanced bandwidth is presented both numerically and experimentally. The MMA is realized by assembling three simple square loops in a three-layer structure according to the idea of separating electric and magnetic resonances. Different from one-layer MMA, the proposed MMA can effectively couple with the electric and magnetic components of the incident wave in different positions for fixed frequency, while, for different frequencies, it can trap the input power into different dielectric layers and absorb it in the lossy substrate. Experimental results indicate that the MMA exhibits a bandwidth of absorbance above 90% which is 4.25 times as that of one-layer MMA, and 10 dB RCS reduction is achieved over the range of 4.77-5.06 GHz. Moreover, the cell dimensions and total thickness of the MMA are only 0.17λ and 0.015λ, respectively. The low RCS properties of the MMA are insensitive to both polarization and incident angles.
Common mode current induced on cable attached to a PCB has been a well-known source of unintentional radiated emissions. The coupling mechanism of the common mode current to the cable can be divided into two types: voltage-driven and current-driven. In voltage-driven mechanism, the common mode current is induced by electric field that couples from traces on PCB to the cable. Previous work showed that these radiated emissions can be estimate based on the self-capacitance of the trace and the signal return plane but the method is only reasonably accurate at lower frequency. This paper develops a model which gives an extended frequency range up to 800 MHz. The formulation for the equivalent common-mode voltage source is improved by taking into account the driving point impedance of the cable which behaves as a wire antenna. The radiated emissions estimated by the improved model match well with the values from 3D electromagnetic simulation of the original PCB with attached cable. It represents an improvement compared to earlier model by 11 dB at 400 MHz to 16 dB at 700 MHz for board size of 10 cm x 16 cm and cable length of 3 m. Similar improvements are obtained for other combinations of board size and cable length. The results show that the cable length is an important factor, in addition to the board area as suggested by earlier work, in determining the magnitude of the equivalent common-mode voltage source. Resonant of the wire antenna affects not only the radiated electromagnetic field but also the commonmode voltage source magnitude due to varying antenna impedances.
In this paper, a hybrid multiobjective evolutionary algorithm, MOEA/D-GO (Multiobjective Evolutionary Algorithm Based on Decomposition combined with Enhanced Genetic Operators), is proposed for fragment-type antenna design. It combines the ability and efficiency of MOEA/D to deal with multiobjective optimization problems with the specic character of two-dimensional chromosome coding of genetic algorithm. And enhanced genetic operators are also introduced to generate new individuals. Numerical results of a set of six multiobjective 0/1 knapsack problems show that MOEA/D-GO with weighted sum decomposition approach outperforms original MOEA/D and MOEA/D-PR (MOEA/D combined with Path-Relinking operator). Then it's applied to optimize a CPW-fed monopole antenna to achieve band-notch characteristic. Both numerical and test results show that MOEA/D-GO is promising for solving multiobjective optimization problems about fragmented antenna.