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To facilitate the analysis of large problems, in this paper, all the full matrices are stored in a sparse form and the PFFT method is employed to accelerate all the matrix-vector products appearing in both hand sides of the matrix equation for the moments. The present method can deal with much larger problems than the traditional MoM-AWE method since the PFFT achieves great reduction in memory requirement...
This work presents a method to determine the required discrete surface distortions to correct errors. The algorithm starts by discretizing the entire reflector surface into triangular patches then by finding a linear relationship between the local distortion and the difference of the distorted and undistorted far fields patterns. A linear system of equations with the distortions as unknowns results...
The characteristic basis function method (CBFM) (V.V.S. Prakash and R. Mittra, 2003) embodies an efficient way to handle large electromagnetic problems in a rigorous manner by defining a reduced set of precomputed characteristic basis functions (CBFs), which represent the currents along the target surface. By utilizing the CBFs, the number of unknowns which arise in the application of the conventional...
This paper investigates the effects of varying the order of RBF's. It has been found that as the order is increased, the accuracy also increases. The accuracy was even shown to increase to the extent that less than 10% of the basis functions were required to obtain the same level of accuracy. However, it is also found that increasing the order also generally increases the condition number of the system...
Marching on in time MOT-based electric field integral equation (EFIE) solvers represent an increasingly appealing avenue for analyzing electromagnetic transients on multiscale and geometrically complex circuits and antennas. Unfortunately, time-domain EFIEs discretized via marching on in time (MOT) recipes suffer from a dense-grid breakdown phenomenon whenever the time step becomes large compared...
In this talk we study properties of electromagnetic integral equations of the first (EFIE) and second kind (MFIE) and show that the solution accuracy and matrix conditioning are almost opposite properties. A smooth operator (EFIE) leads to a better solution accuracy, but poorer matrix conditioning, and a singular operator (MFIE) behaves vice versa. A compromise between solution accuracy and matrix...
In this paper, we develop a time-domain layered finite element reduction recovery (TD-LAFE-RR) method to solve large-scale IC design problems at high frequencies. This method rigorously reduces the matrix of the original multilayer system to that of a single-layer no matter how large the original problem is. More importantly, the matrix reduction is achieved analytically, and hence the CPU and memory...
In this paper, a numerical approach to incorporating a feed-network modeling into the TDFEM analysis of antennas is described. In this approach, a feed network is considered as a multi-port linear passive system, which is connected to the source and the antennas solely through several ports. Based on an appropriate numerical method, a simplified circuit model for this system can be established and...
The paper reports on investigations into semi-blind channel estimation for a 2times2 multiple input multiple output (MIMO) system employing the Alamouti coding scheme. The proposed technique is based on an iterative version of Maximum Likelihood technique and uses a suitable weighting of channel matrices in the current and last iterations. In the presented investigations, it is assumed that the channel...
Phased array system is used to scan an antenna beam to given angles in space. It consists of multiple stationary antenna elements, which are fed coherently, and uses variable phase shifter at each element. The phase shifter is one of the main parts of phased array antennas but it causes loss and complexity is making it. Inevitably, recent demands for highly flexible array control have highlighted...
The authors have proposed 1 m2-ordered plasma equipment using slotted waveguide arrays. Microwave at 2.45 GHz is used for the excitation. Design for uniform aperture electromagnetic (EM) field distribution on the vacuum window is succeeded by the generalized scattering matrix (GSM)- method of moments (MoM) analysis by neglecting plasma. Even if the uniform EM distribution is obtained, the realization...
This paper outlines the advantage of applying domain decomposition to arbitrary surfaces via a multilevel geometry description (MLGD). By constructing the desired simulation surface from embedded lists of subsurface location vectors and orientation matrices; storage, compute, and matrix fill time formulations can be significantly reduced. We discuss proper formation of a multilevel geometry and outline...
This communication focuses on the problem of reducing the computational cost of generating the reduced matrix in the context of CBFM for very large scatterers using two different approaches: (i) MLFMM to compute the far-field interactions between distant functions; and (ii) stabilized bi-conjugated gradient method (BiCGM) to solve the reduced matrix equation iteratively. Additionally, the CBFM is...
In this work, we propose a preconditioner that approximates the dense system operator. For this purpose, we develop an approximate multilevel fast multipole algorithm (AMLFMA), which performs a much faster matrix-vector multiplication with some relative error compared to the original MLFMA. We use AMLFMA to solve a closely related system, which makes up the preconditioner. Then, this solution is embedded...
In this work, a combination of the two methods mentioned above is used in order to find a matrix that maps the response without mutual coupling effects to the response with mutual coupling effects. This work assumes the coupling matrix is Toeplitz and uses a few observations in order to estimate the matrix. The remainder of this paper provides the formulation of the problem for a linear array, results...
Multiple input multiple output (MIMO) wireless communication systems have been a focus of interest, due to their ability to increase the capacity in rich scattering environments by using multi-element antenna arrays both at the transmitter and the receiver sides. However, when dealing with multi-element antenna arrays, effects of mutual coupling among the array elements become significant and should...
The multilevel fast multipole algorithm (MLFMA) has gained substantial interest as a method to accelerate the matrix-vector product in the iterative solving of electromagnetic scattering problems. Its complexity of O(N) or 0(N log N) allows for the simulation of very large scale problems when sufficient computational resources such as parallel computers are available. However, the derivation of a...
In this paper, a new solution to improve the correlation matrix of two closely spaced antennas is illustrated. Contrary to the use of a decoupling network, a physical separator between the antennas is considered. And hence, the use of a metallic plane (PEC) and a metamaterial surface (with bidirectional PMC response) are compared in terms of correlation matrix improvement and radiation patterns.
In the study, we present a novel directions of arrivals (DOAs) estimation by using signal subspace structure of an uniform linear array. The proposed method resolves the directions by using the eigenanalysis of a square matrix formed by the eigencomponents in the signal subspace of data correlation matrix. Simulation results validate the high resolution capacity and fast convergence rate of the proposed...
A stable solver of the time domain integral equation (TDIE) methods with quadratic B-spline temporal basis functions (TBFs) for analyses of transient radiation and scattering problems is proposed. This TBF permits consistent approximations of the induced currents and charges, leading to proper representations of the fields contributed by both the vector and scalar potentials. This TBF also has the...
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