Huapeng Zhao

Efficient Modeling of Three-Dimensional Reverberation Chambers Using Hybrid Discrete Singular Convolution-Method of Moments

Efficient modeling of a three-dimensional reverberation chamber (RC) is achieved by combining the discrete singular convolution (DSC) method and the method of moments (MoM). An RC usually consists of a metallic cavity and one or two conducting stirrers, whose size is normally small compared to the chamber size. The large cavity is efficiently modeled by the DSC method, and the stirrer is simulated by the flexible MoM. Exploiting the property of RWG basis, solutions from the two methods are combined together using the equivalence principle. The validity and advantages of the proposed hybrid technique are shown through comparisons with the commercial software FEKO. Employing the high efficiency of the DSC method, the hybrid technique can analyze one stirrer position of a medium-sized RC in a few hundred seconds on a single personal computer, for which FEKO needs thousands of seconds CPU time. The memory requirement of the proposed method is also less than that of FEKO. Furthermore, our hybrid method provides efficient calculation of electric field strength at a large number of field points, which is of great interest in RC analysis. Simulations show that our method only takes 1.7 seconds to compute electric field strength at 4026 field points.

Hybrid Discrete Singular Convolution-Method of Moments Analysis of a 2-D Transverse Magnetic Reverberation Chamber

In this paper, a new hybrid technique combining the discrete singular convolution (DSC) method and the method of moments (MoM) is proposed for efficient analysis of a 2-D transverse magnetic reverberation chamber. The metallic stirrer is viewed as a current sheet along whose surface the tangential electric field is forced to zero. The DSC method is used to model the cavity excited by the original source plus the current sheet, which are expressed on the grids of the DSC method using the regularization technique. The MoM is used to enforce the boundary condition along the stirrer. Solutions from the aforementioned two steps are coupled together with the aid of the equivalence principle. The validity and advantage of the proposed hybrid technique is shown through comparisons with results from alternative methods. Taking advantage of the high efficiency of the DSC method, the new hybrid technique is shown to be a lot more efficient than a pure MoM with approximately the same memory cost.

Weighted Laguerre Polynomials-Finite Difference Method for Time-Domain Modeling of Thin Wire Antennas in a Loaded Cavity

A weighted Laguerre polynomials (WLP)-finite difference method is proposed in this letter for the fast time-domain modeling of thin wire antennas in a lossy cavity. The modified telegraphers equations (MTE) are used to describe a thin wire antenna, and a rather fine grid is required at the feed point for accurate input impedance calculation. In that case, eliminating the Courant Friedrich Lewy (CFL) limit is important to speed up the calculation. By expressing transient behaviors of field, current, and voltage using global WLP temporal bases, a marching-on-in-degree scheme is obtained through the orthogonality of WLP bases. Without the CFL stability condition, the proposed method is more efficient than conditionally stable finite-difference time-domain (FDTD) method, which requires a large number of time-steps for computing the solution when a very fine grid is used in the spatial mesh. Simulated results are presented and discussed to demonstrate the advantages of the proposed method.

Support Vector Regression for Basis Selection in Laplacian Noise Environment

We demonstrate that the objective function of a basis selection problem in Laplacian noise environment falls into the framework of support vector regression (SVR), and, by iteratively solving a convex quadratic programming (QP) problem that guarantees a globally optimal solution, the sparse solution to the inverse problem can be found. The effectiveness of the proposed algorithm is verified via the application to direction-of-arrival (DOA) estimation. Different from the existing DOA estimation method based on SVR, the proposed algorithm is applicable with single snapshot and does not have to know the number of the sources. Meanwhile, the method does not require a large number of training sets, which in turn decreases the computational complexity.

Diagnosis of Array Failure in Impulsive Noise Environment Using Unsupervised Support Vector Regression Method

Fast and accurate diagnosis of array failure is important for the maintenance of array antennas. Locations of failing elements are usually detected using near field data, which may be polluted by noises. Most existing diagnosis methods assume non-impulsive noise in the measurement data. However, the practical measurement environment may contain impulsive noises, which has not been considered in existing methods. This work proposes to impose a penalty function in the residual between the measured and recovered near field. The impulsive noise in the near field data can then be suppressed by using an appropriate function as the penalty function. Furthermore, minimum ℓp-norm is imposed on the excitation vector. The condition imposed on the noise and the minimum ℓp-norm constraint on the excitation vector constitutes an optimization problem, which is solved using the unsupervised support vector regression. The proposed method is more accurate than existing methods when impulsive noise presents in the near field data, and it is able to deal with a wide range of number of failing elements by adjusting the value of p. Numerical results are presented to show the advantages of the proposed method and to study the choice of p.

Memory-Efficient Modeling of Reverberation Chambers Using Hybrid Recursive Update Discrete Singular Convolution-Method of Moments

A hybrid method is proposed for memory-efficient analysis of reverberation chambers (RCs). In the hybrid method, the cavity is modeled by the recursive update discrete singular convolution (RUDSC) method, and antennas and stirrers inside the cavity are simulated using the flexible method of moments (MoM). In order to solve DSC and MoM unknowns separately, a layer-based elimination algorithm is utilized to eliminate the DSC unknowns. The MoM unknowns are then solved by a direct solver. Once the solution for the MoM model is obtained, the original RC is equivalent to a cavity excited by known current sources. The equivalent problem is finally solved using the RUDSC method. Taking advantage of the layer-based elimination algorithm and the recursive update technique, the memory requirement of the new hybrid method is much smaller than that of using a direct solver. Numerical simulations are presented to show the efficacy of the proposed method. It is shown that the the proposed method substantially reduces the memory cost of RC modeling, which extends RC analysis to higher frequencies.

Modal - Expansion Analysis of a Monopole in Vibrating Reverberation Chamber

A modal-expansion method is proposed for the analysis of a monopole antenna in a vibrating reverberation chamber. Inside the chamber, electromagnetic fields are expanded using modal functions. Mode matching process is applied to enforce the boundary conditions at regional interfaces. Boundary conditions on the four side walls of the chamber are imposed by the point matching method. Combining these two matching processes, a set of matrix equations are obtained and the expansion coefficients can then be determined accordingly. The loss from the chamber walls is accounted for through homogeneous material filling. The input impedance and scattering parameter of a monopole in a reverberation chamber are computed and statistical analysis of the scattering parameter is conducted when one of its walls is vibrating.

Modal Characteristic Basis Function Method for Solving Scattering From Multiple Conducting Bodies of Revolution

The analysis of scattering from multiple bodies of revolution (BoRs) has important applications in microwave remote sensing, radar imaging and other areas. For single BoR, three dimensional problem can be degenerated into 2.5 dimensional problem based on the modal Green functions (MGFs), reducing the solving time and storage remarkably. However, it is difficult to extend the MGF to multiple arbitrarily orientated BoRs. This paper presents a modal characteristic basis function method for solving the scattering from multiple BoRs. It combines the MGF of BoR with the characteristic basis function method, named as the BoR-CBF method. Here, the MGF of BoR is first applied to efficiently solve the current distribution on the surface of each BoR. The singular value decomposition is then used to construct the global modal characteristic basis functions (MCBFs) for each BoR. Finally, the MCBFs are transformed into the RWG basis functions using a basis function mapping technique so that the filling of the interaction matrix can be accelerated by the multilevel fast multipole algorithm. By using the BoR-CBF method, the scattering of multiple arbitrarily orientated BoRs can be solved efficiently. Numerical results are presented to demonstrate the accuracy and efficiency of the BoR-CBF method.

Domain Decomposition Method Based on Integral Equation for Solution of Scattering From Very Thin, Conducting Cavity

In this communication, a novel domain decomposition method (DDM) based on integral equation is developed for solving scattering problems of very thin, conducting cavity. By imposing equivalent electric and magnetic currents on the aperture, the original problem is transformed into interior and exterior problems. Different from traditional method based on interior-exterior equivalence principle, this work couples the exterior and interior problems only through the transmission condition on the aperture. Based on this DDM, a well-posed combined field integral equation (CFIE) is successfully developed to realize fast solution of electromagnetic scattering from open-ended cavity with extremely thin or zero thickness. Compared to the electric field integral equation, the proposed CFIE significantly improves the convergence rate of iterative solvers. Numerical results are given to demonstrate the validity and advantages of the present method.

Installed Radiation Pattern of Patch Antennas: Prediction based on a novel equivalent model.

A simple but efficient equivalent model of patch antennas is proposed for predicting the radiation pattern of patch antennas on large platforms. The equivalent model is constructed based on the radiation mechanism of a patch antenna. Only three design parameters need to be optimized, making the model more computationally efficient than those equivalent dipole models for general problems. After the equivalent model is optimized with a differential evolution (DE) algorithm, it is further installed on a platform to compute installed radiation patterns. Simulation results show that the installed radiation patterns of both a single element and an array can be accurately predicted using the equivalent model, where the root-mean-square errors (RMSEs) are less than 0.94%. The proposed equivalent model method does not require detailed geometry information of the patch antennas. Furthermore, it avoids direct modeling of antenna structures, leading to a drastic reduction in computation and storage costs.