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IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, VOL. 00, NO. 00, 2016 1
A Hybrid Solver Based on Domain Decomposition
Method for the Composite Scattering
in Layered Medium
1
2
3
Yi Ren, Member, IEEE, Wei-Feng Huang, Jun Niu, and Qing-Huo Liu, Fellow, IEEE4
Abstract—In the framework of domain decomposition method,5
we present a novel hybrid solver for accurate electromagnetic6
simulations of composite objects in layered medium (LM). This7
hybrid solver combines the surface integral equation method and8
the finite element method to effectively minimize the simulation9
domain, where the effect of inhomogeneous background is10
involved by the LM Green’s functions, and the field transmission11
between neighboring subdomains is realized by the Riemann12
solver. Numerical results are given to validate the proposed solver.13
Index Terms—Finite element method (FEM), layered medium,14
surface integral equation (SIE).15
I. INTRODUCTION16
D
OMAIN decomposition method (DDM) is one of the most17
popular research topics in electromagnetic engineering.18
DDM generally divides a complex domain into several smaller19
subdomains and solves them separately. DDM has been exten-20
sively investigatedforfree-spaceapplications, but its application21
in layered medium (LM) is rarely reported. The application of22
DDM is much more difficult in LM than in homogeneous back-23
ground due to the involved complex background for the former.24
As a result, the DDM for LM applications is still a challenging25
topic.26
DDM was first developed for the finite element method (FEM)27
[1] and the finite-difference time domain (FDTD) [2], and then28
extended to the surface integral equations (SIEs) [3]. DDM with29
FEM or FDTD is only efficient in homogeneous background30
simulations, rather than in LM simulations. This is because an31
intrinsic disadvantage of FEM and FDTD is the large truncation32
domain for the simulation in inhomogeneous background, which33
leads to a heavy computational workload. SIE is more suitable34
for LM simulations since it only needs to discretize the target35
surface and the effect of background is involved by the layered36
medium Green’s functions (LMGFs) [4]. Unfortunately, SIE37
is only feasible for the homogeneous target. Therefore, a good38
option is to combine their advantages and avoid their drawbacks.39
Namely, FEM is utilized to simulate the interior domain, while40
Manuscript received February 16, 2016; accepted June 08, 2016. Date of pub-
lication; date of current version. This work was supported in part by the NSFC
under Grant 61301032, the Natural Science Foundation of Chongqing under
Grant cstc2013jcyjA40037, and the Scientific and Technological Research Pro-
gram of Chongqing Municipal Education Commission under Grant KJ130531.
Y. Ren is with the Chongqing University of Posts and Telecommunications,
Chongqing 40065, China (e-mail: renyi_cq@hotmail.com).
W.-F. Huang, J. Niu, and Q. Liu are with the Department of Electrical and
Computer Engineering, Duke University, Durham, NC 27705 USA (e-mail:
hwfbreeze@gmail.com; jn92@duke.edu; qhliu@duke.edu).
Color versions of one or more of the figures in this letter are available online
at http://ieeexplore.ieee.org.
Digital Object Identifier 10.1109/LAWP.2016.2582149
SIE is utilized to simulate the surface domain. It should be 41
pointed out that we are aware of very few literature reports 42
on this topic in LM applications [5], [6], and all the existing 43
papers about the hybrid SIE/FEM only focus on the conformal 44
mesh, rather than DDM with nonconformal mesh. Thus, a more 45
attractive scheme is the hybrid FEM/SIE based on DDM with 46
nonconformal meshes. 47
This letter combines DDM with SIE and FEM to present 48
a hybrid solver for the accurate electromagnetic simulation of 49
composite objects in LM. In this hybrid solver, simulation do- 50
main is divided into one surface domain and several volume sub- 51
domains. The surface domain is modeled by SIE with LMGFs, 52
whereas the volume subdomains are modeled by FEM. The Rie- 53
mann solver boundary condition is utilized to connect the fields 54
on different subdomain interfaces [7], [8]. The resulting matrix 55
equation is solved by the Krylov subspace solver with precon- 56
ditioning method [9], [10]. Numerical results are then given to 57
validate the accuracy of this hybrid solver. 58
II. FORMULATION 59
Suppose a composite object with permittivityε(r) and perme- 60
ability μ(r) immersed in a planarly LM. The simulation domain 61
is decomposed into N
Sub
i
FEM subdomains and one SIE do- 62
main. In the ith interior FEM subdomain, the fields E
Ω
i
and 63
H
Ω
i
can be formulated into an equivalent variational problem, 64
i.e., 65
F (E
Ω
i
)=
1
2
Ω
i
1
μ
r
∇×E
Ω
i
·
∇×E
Ω
i
− k
2
0
ε
r
E
Ω
i
·E
Ω
i
dV
+ jk
0
∂ Ω
i
E
∂ Ω
i
×
¯
H
∂ Ω
i
· ˆndS,
i =1,...,N
Sub
i
(1)
where ˆn denotes the outward unit normal vector on ∂Ω
i
, and k
0
66
is the free-space wavenumber.
¯
H
i
= Z
0
H
i
, and Z
0
is the free- 67
space intrinsic impedance. When the curl-conforming bases are 68
used to expand the fields, we have 69
E
Ω
i
=
N
Ω
i
m =1
E
Ω
i
m
f
m
¯
H
Ω
i
=
N
Ω
i
m =1
H
Ω
i
m
f
m
(2)
where N
Ω
i
is the degrees of freedom (DOF) in Ω
i
, and {f
m
} 70
are the curl-conforming bases. E
Ω
i
m
and H
Ω
i
m
are the expansion 71
coefficients of E
i
and
¯
H
i
, respectively. A standard Galerkin 72
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