999
Fast calculation of bistatic RCS for conducting
objects using the adaptive cross approximation
algorithm
Lei Chen
#1
, Yufa Sun
#2
, Shuaishuai Yang
#3
#
Key Lab. of Intelligent Computing & Signal Processing, Ministry of Education, Anhui University
Hefei, P.R. China
1
546502218cl@sina.com
2
yfsun@ahu.edu.cn
3
yangshuai918@yahoo.com.cn
Abstract— Adaptive cross approximation (ACA) algorithm as a
kind of common matrix compression method is often used to
analyze the electromagnetic radiation and scattering problems.
In the region of far field, the impedance matrix is compressed by
ACA method, and the extracted impedance matrix is accelerated
filling by equivalent dipole-moment method (EDM). In the area
of near field, the method of moments or the equivalent
dipole-moment method is applied for filling the impedance
matrix. The iterative near field preconditioning technique is used
to solve matrix equation, so that fast calculation of radar cross
section (RCS) can be achieved. Numerical results show that the
computational efficiency is improved significantly via applying
the presented method in this paper without sacrificing much
accuracy.
Keywords—
adaptive cross approximation algorithm; equivalent
dipole-moment method; near field preconditioning; radar cross
section
I. INTRODUCTION
With the development of computational electromagnetics,
method of moments (MOM) [1] as a representative of the
integral equation methods has been widely applied to the
analysis of the electromagnetic scattering problems. The
method owns a wide application range and produces higher
calculation accuracy. But with the electric size of the object
increasing, the consumption of the memory and time has
synchronously increased dramatically. Therefore, we usually
adopt matrix compression method to save memory and
computing time, in order to calculate the RCS easily. At
present, the main methods of matrix compression include
single IE-QR [2] method, UV multilevel partitioning method
[3] and multi-layer matrix decomposition algorithm (MLMDA)
[4], etc. This paper introduces a kind of method based on
matrix compression--adaptive cross approximation (ACA)
algorithm[5],[6] and combined with equivalent dipole-moment
technology [7],[8] to achieve the rapid filling of impedance
matrix element. In the while, the near field preconditioning
technique [9] is used to accelerate the solution of matrix
equations.
II. T
HEORY
A. Adaptive Cross Approximation algorithm
Recently, the adaptive cross approximation algorithm has
been proposed to reduce the computational complexity of
integral equation solvers. ACA is based on matrix
compression method and takes advantage of the rank-deficient
nature of the coupling matrix blocks representing
well-separated MOM interactions. The beauty of the ACA
algorithm is its purely algebraic nature and independent of
Green’s function. The ACA algorithm presented herein is
based on constructing octree model and dividing basis
functions into groups, which leads to realize the impedance
matrix decomposition into a series of different submatrices.
Among, the diagonal blocks, which correspond to self-group
interactions, as well as matrix blocks resulting from the
interactions of two touching groups, are regarded as rank-full
matrices. The off-diagonal blocks which describe remote
interactions are close to some low-rank matrices, it might be a
good idea to approximate them by low-rank matrices. Thus,
we use the ACA algorithm to carry on the effective
compression. Applying the algorithm to get the two dense
rectangular matrices
U andV , we only need to fill and store
matrix of the rows and columns.
Let the rectangular matrix
mn
Z
u
represents the coupling
between two well-separated groups in the MOM computation
domain. The ACA algorithm aims to approximate
mn
Z
u
as
mn
Z
u
with a prescribed accuracy. Particularly the ACA
algorithm constructs the approximated matrix
mn
Z
u
through a
product form, namely:
11
1
r
mn mr rn m n
ii
i
ZUV uv
uuu uu
¦
(1)
where
r
is the effective rank of the matrix
mn
Z
u
. The goal
of the ACA is to achieve:
mn mn mn mn
RZZ Z
H
uuu u
d
(2)
Where
mn
R
u
is termed the error matrix and
H
is a given
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978-1-4673-1800-6/12/$31.00 ©2012 IEEE