Nie Zaiping

On the improvement of the mutual coupling compensation in DOA estimation

A new and exact calculation method for the mutual impedance matrix of receiving arrays is proposed. The mutual impedance matrix is derived from electromagnetic boundary conditions and can be used to relate the coupling free open-circuit voltages, instead of the conventional ones, to the measured voltages. A remarkable improvement on compensation for the coupling effects is shown in the direction finding applications, while a simple relationship between measured terminal voltages and the coupling free voltages is remained.

Solving 3D electromagnetic scattering and radiation by local multilevel fast multipole algorithm

As the fastest integral equation solver up to now, multilevel fast multipole algorithm (MLFMA) has been applied successfully to solve electromagnetic scattering and radiation from 3D electrically large object. But for very large scale problems, the storage and CPU time required in MLFMA are still expensive. In this paper, a local multilevel fast multipole algorithm (LMLFMA) is proposed to further speed up the efficiency of MLFMA in conjugate gradient (CG) iteration. In the LMLFMA, only the local interactions between the subscatters are taken into account. And, the interaction regions in iteration are varying adaptively with iterative current density. With decrease of iterative error, iterative current density tends to real one, the interaction regions required are diminishing. When the iterative error is less than a critical iteration error, only the interaction between nearby regions at the finest level is considered. Numerical results show that the LMLFMA has good accuracy, and much better efficiency than traditional MLFMA.

DOA estimation using music algorithm on a cylinderical conformal array

A modified method for DOA estimation on a cylinderical conformal array is proposed. Through dividing an array into 8 subarrays, MUSIC algorithm can be applied in cylinderical conformal array for DOA estimation. This method can also be used in any other curve conformal geometries. Simulation results demonstrate the efficiency and accuracy of the proposed method.

A 3-D ray-propagation multilevel fast multipole algorithm using an adaptive technique

The 3-D vector electromagnetic scattering problem is solved efficiently by a ray-propagation multilevel fast multipole algorithm (RP-MLFMA). An adaptive technique is developed to control the computational complexity and the accuracy. Numerical results are given to verify the efficiency of the present algorithm.

Solving Scattering from Multiple Conducting Objects by Hybrid Multi-Level Fast Multi-Pole Algorithm with Generalized Forward-and-Backward Method

Abstract To speed up the solution of scattering from multiple conducting objects with complex structures, a hybrid multi-level fast multi-pole algorithm with a generalized forward-and-backward method is developed. The region involving multiple conducting objects is divided into finite uniform sub-regions. The induced current in each sub-region is solved iteratively by a generalized forward-and-backward method. The interactions between sub-regions and the iterative current in each sub-region are computed by the multi-level fast multi-pole algorithm. The present method has only the memory requirement of O(NmaxlogNmax), where Nmax is the maximum number of unknowns located in these sub-regions. Numerical results demonstrate the efficiency and accuracy of the present method for multi-object scattering problems.

Numerical mode matching method with perfectly matching layer

The numerical mode matching method (NMM) with the perfectly matching layer (PML) has been presented in this paper to solve electromagnetic fields in stratified media with some possible lossless layers. When the 2D inhomogeneous media is lossy media, the field in this inhomogeneous media can be solved efficiently by using the NMM with the concepts of the general reflection matrix and general transmission matrix. Unfortunately, this method failed in the case of lossless media. In order to make the NMM available in the media with lossless layers, the PML has been introduced into the NMM in this paper to build the truncated absorbing boundary in lossless layers. Some numerical examples have also been given in this paper.

Spatial fading correlation of circular antenna arrays with Laplacian PAS in MIMO channels

The analytic expressions of spatial fading correlation for uniform circular arrays (UCA) in MIMO (multiple-input multiple-output) channels with clustering scattering have been derived, and the spatial correlation with a power azimuth spectrum (PAS) of Laplacian distribution is evaluated.

A local multilevel fast multipole algorithm for 3D electromagnetic scattering

A local multilevel fast multipole algorithm (LMLFMA) is proposed to further speed up the efficiency of the multilevel fast multipole algorithm (MLFMA), which is used to expedite the computation of matrix-vector multiplication in conjugate gradient iteration. In the present method, the coarsest level is determined by the iterative error. And at the coarsest level, the interaction between far regions is omitted. When the iterative error is less than the critical iteration error, only the interaction between nearby regions is considered. Numerical results show that the LMLFMA has a reasonable accuracy, and higher efficiency, compared with the MLFMA combined with the partly approximation iteration (PAI) technique. So it is very efficient for solution of scattering from 3D targets with electrically large sizes.

Partly approximate iteration technique for accelerating CG-MLFMA solution

To further expedite the solution of the conjugate gradient iteration multilevel fast multipole algorithm (CG-MLFMA), we have developed a partly approximate iteration technique. When the iterative error is lower than the critical iteration error (CIE), the matrix-vector multiplication can be computed approximately by the interactions from the nearby region. The CIE is determined by the contributions of the nearby region and the accuracy required. Compared to the interactions from the non-nearby region, the interactions from the nearby region only possess a very small portion of the total complexity. Because the number of iterations needed in the presented method does not increase dramatically, total CPU time can be reduced greatly. Numerical results are given to demonstrate the validity and efficiency of the presented method.

Efficient solution of 3-D vector electromagnetic scattering by FMM with partly approximate iteration

The fast multipole method (FMM) with partly approximate iteration is developed for efficient solution of EM scattering from a conducting object with large electrical size. An appropriate critical iterative error (CIE) is used to switch the FMM into approximate calculations, in which only the contributions from nearby groups are considered. The present method can solve efficiently not only the bistatic RCS of an object but also the monostatic RCS of an object It can also be combined with other efficient techniques to achieve a faster algorithm.