Asymptotic Waveform Evaluation Research Articles

Broadband RCS Acquisition by Finite Periodic Arrays Using the Characteristic Basis Function and Asymptotic Waveform Evaluation

Broadband RCS Acquisition by Finite Periodic Arrays Using the Characteristic Basis Function and Asymptotic Waveform Evaluation

Internet Data Bandwidth Optimization and Prediction in Higher Learning Institutions Using Lagrange’s Interpolation: A Case of Lagos State University of Science and Technology

Episodic edifices have a diversity of significant solicitations in contemporary machineries and engineering owing to their exclusive electromagnetic properties. Frequently used episodic edifices comprise; occurrence selective surfaces, visual grilles, phased collection projections, photonic bandgap supplies, and numerous metamaterials. The scrutiny of episodic edifices has all the time been a significant area in computational electromagnetics. This episode, describes a precise and effectual arithmetical study, grounded on a higher-order finite element method (FEM), for depicting the electromagnetic properties of an episodic edifices. Grounded on the Floquet theory, episodic frontier conditions and radioactivity conditions are foremost resultant for the unit cell of an episodic edifice. The FEM is formerly applied to unravel Maxwell’s reckonings in the unit cell. To augment the precision and effectiveness of the FEM, rounded elements are employed to discretize the unit cell and higherorder course basis functions are used to enlarge the electrical arena. The asymptotic waveform evaluation (AWE) is applied to implement wild frequency and rawboned curves. To prove the proficiency of the projected FEM, we apply it to the scrutiny of episodic absorbers, incidence selective edifices, and phased collection aerial. For the aerial analysis, a severe waveguide port condition is industrialized to precisely model the aerial feed edifices. In all the occurrences premeditated, acceptable outcomes are obtained. Key words : Episodic, edifice, absorbers, waveguide, electromagnetic. DOI : 10.7176/CEIS/10-1-04

MWCAWE: A multivariate WCAWE approach for parametric model order reduction, and a sampling strategy for the bivariate case

In this paper, the multivariate well-conditioned asymptotic waveform evaluation (MWCAWE) algorithm is presented. It is based on a univariate version of the algorithm, previously introduced for fast frequency sweeps. Taking advantage of the robustness of this univariate algorithm, the MWCAWE enables to effectively generate multi-parameter reduced-order models. Additionally, a residue-based contour following approach is introduced for a two-stage generation of a projection basis, here applied on bi-variate acoustic problems where frequency and a material parameter are in focus. The effectiveness of the proposed method is demonstrated on two poro-acoustic problems, highlighting both the good convergence property of the algorithm and the potential of the multi-patch strategy for parametric applications.

An Evaluated PMCHWT Solution of EM Scattering for Mutimedium Targets With Variant Permittivities

An evaluated PMCHWT is formulated in terms of the asymptotic waveform evaluation (AWE) technique to predict the scattering characteristics of multi-medium targets. At first the uncertain dielectric constant can vary within a certain range by setting it as the permittivity variable. Then the evaluated PMCHWT is constructed with these permittivity variables. Noted that the inversion of the impedance matrix is needed only once and the moment matching technique is used in the process of recursion. Moreover, the high-order derivatives are applied in order to obtain the greater convergence radius. Finally, the impedance matrix, right vector and the current density are expanded with the Taylor series. And the current density is approximated by the reduced order rational Padé function. Compared with the traditional perturbation method, greater radius of convergence can be obtained by using the proposed method. In addition, higher efficiency can be gotten than the general Monte Carlo (MC) method.

A Fast Frequency Sweep approach for performance-based optimization of earthquake-resistant irregular large-scale buildings

Performance-Based Design (PBD) optimization of buildings subjected to seismic excitations has increasingly been applied to regular small-scale structural systems to minimize initial or life-cycle costs. Nonetheless, a comprehensive bibliographic survey reveals that studies dealing with irregular buildings are scarce, although they can present higher seismic vulnerability than regular buildings. Specifically, the PBD optimization of irregular buildings represented by large-scale finite element (FE) models, and considering dozens of discrete design variables, cannot be found to the best of the authors’ knowledge. Hence, this paper presents an original framework for the PBD optimization of irregular buildings subjected to seismic excitations, handling thousands of DOFs and dozens of discrete design variables. To relieve the computational burden, enabling the problem to be solved, a Model Order Reduction (MOR) strategy based on the Well-Conditioned Asymptotic Waveform Evaluation (WCAWE) approach is combined with a hybrid optimization algorithm, which integrates a local optimizer with a restart strategy. The former is employed to speed up the frequency-domain response, while the latter allows for tackling a non-convex and multimodal objective function with many discrete variables. The procedure is adaptatively devised to operate in a robust and fully black-box approach. The application case consists of a stiffness in-plane irregular H-shape building with 16,452 active DOFs and 34 discrete design variables. The proposed scheme largely reduces the computational burden, leading to speed-up factors (SUF) up to 19 times compared to direct frequency-domain solutions.

A-EFIE With Model-Order Reduction Technique for Fast Analysis of Circuit Simulation

A fast frequency-sweep method for microwave circuit simulation based on a full-wave solver is presented in this letter. The complexity of the mathematical model of the augmented electric field integral equation (A-EFIE) system is reduced by employing the model-order reduction (MOR) technique, where the reduced-order subspace is constructed by singular value decomposition (SVD). Compared to the A-EFIE with the asymptotic waveform evaluation (AWE) technique, the A-EIFE with the SVD-based MOR technique can speed up the broadband circuit analysis more efficiently.

Asymptotic Waveform Evaluation With Higher Order Poles

The research generalizes the traditional asymptotic waveform evaluation method only with first order poles to the method with higher order poles case. We discuss the invertibility of the induced generalized Vandermonde matrix with the determinant formula of the matrix. Via establishing the equivalence of the multiplicity of the poles and the coefficients of the introduced matrix, the generalized asymptotic waveform evaluation algorithm is built. Then the real system realization of the lower order poles-residues form is asserted. At last two experiments are provided to check the validity of our algorithm.

Research on wide-band electromagnetic scattering characteristics of random distributed objects using Monte Carlo method

In the engineering applications, the distribution of objects is mostly random. Therefore, scattering analysis of randomly distributed objects has been one of the important problems in broadband electromagnetic calculation field. To resolve the problem, the Asymptotic Waveform Evaluation technique in conjunction with Monte Carlo Method is presented. First, the stochastic distribution is modeled by the Monte Carlo Method, and then the Asymptotic Waveform Evaluation technique using Padé approximation is utilized to achieve the Radar Cross Section at a wide frequency band. Numerical results show that the Asymptotic Waveform Evaluation technique can solve the random distributed object problems efficiently and accurately.

A Combined Asymptotic Waveform Evaluation and Random Auxiliary Sources Method for Wideband Solutions of General-Purpose EM Problems

An asymptotic waveform evaluation (AWE) formulation for the random auxiliary sources (RAS) method is presented to solve general-purpose electromagnetic (EM) problems. The susceptibility of the RAS-AWE procedure to numerical noise is studied. A singular value decomposition solution is proposed to improve the possible obtained bandwidth. The solution parameters are studied for 2-D and 3-D problems. Also, the limitations of the proposed formulation are discussed in comparison to the method of moments (MoM). Furthermore, several general EM scattering problems are solved using the proposed RAS-AWE procedure to assess the performance and accuracy compared to other formulations. General observation points are discussed to highlight the advantages and disadvantages of the proposed approach. In addition, the core kernel operators are presented for the 2-D, 3-D, and waveport formulations.

Application of Compressive Sensing to Asymptotic Waveform Evaluation for Fast Frequency-Sweep Analysis of Electromagnetic Scattering Problems

To reduce the computing resource of full-scale impedance matrix and its high-order derivatives in traditional Asymptotic Waveform Evaluation (AWE), compressive sensing (CS) is applied to AWE for fast and accurate frequency-sweep analysis of electromagnetic scattering problems. In CS framework, some prior knowledge is extracted by constructing and solving undetermined equation of 0-order surface induced current, so that coefficients about high-order induced current can be accurately obtained by the prior knowledge, and finally the wide-band radar cross section (RCS) is calculated. Numerical results of two-dimensional objects and bodies of revolution (BOR) were presented to the show the efficiency of the proposed method.

Improved Well-Conditioned Model Order Reduction Method Based on Multilevel Krylov Subspaces

Reduced order models (ROMs) based on the asymptotic waveform evaluation enable fast and efficient parametric analysis of large-scale matrix systems exhibiting nonlinear dependence on certain desired parameter(s). However, they are known to be narrowband due to the inherently ill-conditioned moment generation process. While well-conditioned approaches exist that enforce the moment-matching criteria by introducing some correction terms, these are not optimal and are difficult to parallelize. This letter introduces a well-conditioned multilevel Krylov model order reduction (WMKMOR) technique which is accurate over a larger band and faster to set up than existing approaches. Also, the multiple levels of Krylov subspaces in WMKMOR are generated independently. The improvement in ROM bandwidth using this technique is demonstrated for a finite-element model of an electromagnetic scattering example.

Fast simulations of electromagnetic scattering from rough surface over a frequency band using asymptotic waveform evaluation technique: horizontal polarization

The asymptotic waveform evaluation (AWE) technique combined with the scalar integral equation and the tapered plane wave is chosen to fast simulate the electromagnetic scattering from rough surface over a frequency band under horizontal (H) polarization in this paper. The tapered plane wave with the energy in a narrow beam is chosen as the incident wave to avoid the artificial edge diffraction due to the finite length of the simulated rough surface. And the scalar integral equation is used to obtain the surface unknowns along the rough surface induced by the incident wave. The validity and efficiency of the AWE are shown by comparing with the repeated calculation at every finer frequency increment through the method of moments (MoM). The influences of several important parameters, such as root-mean-square height, correlation length and incident angle are studied and discussed. And in this paper, the complex frequency hopping technique is also used to extend the validity of AWE.

New Adaptive Multi-Expansion Frequencies Approach for SP-MORe Techniques With Application to the Well-Conditioned Asymptotic Waveform Evaluation

Fast frequency sweep using model order reduction (MORe) techniques is one of the most valuable and efficient features in high-frequency simulators. These techniques usually use a single full solution at a given frequency to build a smaller approximation reduced model, which might be insufficient for wideband and ultrawideband simulations of high quality factor RF and microwave devices. Despite the fact that many computationally reliable error estimate methods have been presented, they all share the same starting point, which is to estimate the residual error between fast sweep solutions and not the actual error. In this paper, we introduce a new accurate and computationally reliable error estimate approach based on the lossless network condition for the automation of single-point MORe. When applied with the well-conditioned asymptotic waveform evaluation, the new approach shows very good performances in terms of accuracy and computation time compared with existing multipoint MORe and commercial EM software.

Numerical Solution of Diffraction Problems: A High-Order Perturbation of Surfaces and Asymptotic Waveform Evaluation Method

The rapid and robust simulation of linear waves interacting with layered periodic media is a crucial capability in many areas of scientific and engineering interest. High-order perturbation of surfaces (HOPS) algorithms are interfacial methods which recursively estimate scattering quantities via perturbation in the interface shape heights/slopes. For a single incidence wavelength such methods are the most efficient available in the parameterized setting we consider here. In the current contribution we generalize one of these HOPS schemes by incorporating a further expansion in the wavelength about a base configuration which constitutes an “asymptotic waveform evaluation” (AWE). We not only provide a detailed specification of the algorithm, but also verify the scheme and point out its benefits and shortcomings. With numerical experiments we show the remarkable efficiency, fidelity, and high-order accuracy one can achieve with an implementation of this algorithm.

Temperature distribution analysis of piezoelectric transformer with heat couple component

ABSTRACTThe use of a heat transfer structure can effectively improve the power of a piezoelectric transformer (PT). A heat couple component (HCC) serves as the core element in the heat transfer structure and improves temperature distribution of PT. The finite element method and experimental measurement are conducted to determine the influence of HCC to the temperature distribution of PT in this study. The heat sources are mechanical vibration, piezoelectric, dielectric losses of PT, as well as the friction heat. The thermal contact conductance coefficient between HCC and PT is determined by the asymptotic waveform evaluation method.

Analysis of Fourier and Non-Fourier heat conduction using Tiknonov based Well-conditioned Asymptotic Waveform Evaluation Technique

Analysis of Fourier and Non-Fourier heat conduction using Tiknonov based Well-conditioned Asymptotic Waveform Evaluation Technique

Delay Analysis and Design Optimization for Low-Swing RC-Limited Global Interconnects

On-chip global interconnects are becoming speed and power bottlenecks in state-of-the-art chips. Low-swing signaling is used to improve delay performance and reduce power consumption. This paper first performs a delay analysis for different low-swing circuits based on the Asymptotic Waveform Evaluation (AWE). In addition, new delay metrics are presented and analyzed. The new delay metrics demonstrate that optimal designs can be obtained in low-swing signaling. To verify our analysis, a simulation environment is established. The simulation results indicate that the optimal designs can increase the 3[Formula: see text]dB bandwidth of a wire by more than 40% in resistively driven or capacitively driven 10[Formula: see text]mm global links. Thus, these optimal design methods can effectively improve the bandwidth of global wires.

Fast frequency sweep method for indirect boundary element models arising in acoustics

This paper presents an efficient approach for computing frequency sweeps with fine increments of acoustic systems described by the variational indirect boundary element method. The matrices arising from such boundary element discretizations are fully populated and their assembly is computationally demanding as it involves the calculation of double surface integrals for each system matrix entry. Therefore, the two operations performed when computing the response at one frequency, namely assembling the system matrix and solving the associated linear system, may be of the same order of magnitude in terms of the required computational time. The proposed fast frequency sweep approach accelerates both operations. First, it avoids forming the system matrices for each individual frequency. Matrices are only assembled at a few master frequencies, while for the rest, interpolation is used on scaled quantities determined at the master frequencies. Second, it avoids solving a dense linear system at each frequency. Padé approximants constructed via the well-conditioned asymptotic waveform evaluation algorithm are used to extrapolate the response around expansion frequencies using derivative information. The proposed method was tested on an exterior acoustics application representing an academic test case, as well as on an interior/exterior application representing an industrial test case.

Fast Frequency Sweep Using Asymptotic Waveform Evaluation Technique and Thin Dielectric Sheet Approximation

The thin dielectric sheet (TDS) surface integral equation (SIE) combined with the asymptotic waveform evaluation (AWE) technique is proposed to efficiently analyze wideband properties of thin dielectric layers such as radome and composite materials. The TDS SIE is an efficient method for analyzing the thin dielectric layer because the number of unknowns of the TDS SIE is fewer than that of the volume integral equation (VIE) and the condition number of the TDS impedance matrix is small. In addition, the AWE technique based on a Taylor series and the Pade approximation is a well-known method for fast frequency sweep. Therefore, the combination of these two methods makes analysis of the thin dielectric layer efficient in the wide frequency region because the advantages of each method are shown at the same time. In order to determine the valid bandwidth of the approximated results for arbitrary problems using the TDS combined with the AWE, the bandwidth estimation approach for the AWE is applied. The results of the proposed method for closed and open structures agree very well with the exact solutions and reveal the capability for fast frequency sweep.

Fast scattering analysis over a wide frequency band using Clenshaw–Lord‐type Pade–Chebyshev approximation

Pade–Chebyshev approximation of Clenshaw–Lord type with method of moments is proposed for wide-band analysis of an arbitrary-shaped perfect electric conductor structure. Moreover, various Chebyshev polynomials, such as first, third, and fourth kinds, are used to express the singular points in the graph to display the expected result for scattering characteristics. The proposed algorithm has a wide radius of convergence due to the use of Chebyshev polynomials and improves calculation speed because Clenshaw–Lord-type Pade approximation requires fewer sampling points than Maehly-type Pade approximation in the derivation of the rational function. The results of the proposed method agree very well with the exact solution and reveal its possibility of obtaining more accurate solution than the asymptotic waveform evaluation technique.