2436 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 65, NO. 5, MAY 2017
Fast and Efficient Analysis of Radome-Enclosed
Antennas in Receiving Mode by an Iterative-Based
Hybrid Integral Equation/Modified Surface
Integration Method
Binbin Wang, Mang He, Senior Member, IEEE, Jinbo Liu, Chuanfang Zhang, and Houjun Sun
Abstract—An iterative-based hybrid method, which combines
the volume-surface integral equation (VSIE) and the modified
surface integration (MSI) method, is presented to analyze the
radome-enclosed antennas in receiving mode. Compared with the
previously published hybrid approaches, this method improves
computational accuracy by including the effects of shaded wall
of the radome and the mutual interactions between antennas and
radome during the numerical solution of the VSIE in an iterative
manner. By embedding different parts of the antenna-radome
structure (ARS) into three distinct oct-trees, the multilevel fast
multipole algorithm (MLFMA) is used to accelerate both the
VSIE solution and the surface/volume integrations in the MSI
stage. The new method obtains more accurate results than its
original version within less CPU time, and keeps good accuracy
with much less memory usage and computational time when
compared with the MLFMA-accelerated full-wave VSIE solution
for the entire ARS.
Index Terms—Integral equation, iterative method, multilevel
fast multipole algorithm (MLFMA), radome, receiving antenna,
surface integration (SI).
I. INTRODUCTION
R
ADOME has widespread applications in protecting
antennas from adverse environmental effects, but the per-
formance of the enclosed antenna or array will be much or less
altered due to the presence of the radome. Hence, accurate
evaluation of the radome’s effects is essential to the design of
radome-enclosed antennas in practice engineering. A number
of effective solutions have been reported to handle this prob-
lem [1]–[9], including the full-wave solutions [2]–[4], [8], [9],
the high-frequency approximate methods [2], [5], [6], and
the hybrid approaches [1], [2], [7]. However, it is found
that almost all of the existing methods are only proposed
to study the radome effects on antennas in transmitting
mode [2]–[9]. Although in many application scenarios, such
as in telemetry, direction finding, passive guidance, and fire-
control radars [1], [2], antennas usually operate in receiving
Manuscript received September 26, 2015; revised August 26, 2016; accepted
January 28, 2017. Date of publication March 1, 2017; date of current
version May 3, 2017. This work was supported by the National Natural
Science Foundation of China under Grant 61471040. (Corresponding author:
Mang He).
The authors are with the School of Information and Electronics, Beijing
Institute of Technology, Beijing 100081, China (e-mail: hemang@bit.edu.cn).
Color versions of one or more of the figures in this paper are available
online at http://ieeexplore.ieee.org.
Digital Object Identifier 10.1109/TAP.2017.2676718
mode, the development of analysis method for the antenna-
radome structure (ARS) in this commonly used working mode
has received much less attention. In the authors’ viewpoint,
there are two main possible reasons for such delayed research
situation: 1) when full-wave methods are used to analyze ARS
with electrically large size in receiving mode, the computa-
tional burden is still formidable as for the transmitting case,
although the utilization of fast solvers can alleviate the prob-
lem to some extent [14] and 2) on the other hand, existing high
frequency or hybrid methods, which are accurate enough for
the analysis of ARS in transmitting mode, cannot be used for
the receiving mode directly, and the reason can be explained
as follows. In transmitting mode, the equivalent source on the
outer wall of the radome is obtained by direct computations
(the physical optics (PO) method [2]) or by the equivalent
aperture (the aperture integration-surface integration (AI-SI)
method [5]) of radiation fields from the transmit antennas,
and then, far-field pattern of ARS is easily achieved via the
equivalence theorem. Whereas for the analysis of ARS in
receiving mode, the excitation field of the receiving antennas,
which is exactly the transmitted field within the space enclosed
by the radome, should be obtained first. But in this case,
the unique excitation of the ARS is the incident plane wave
and in theory the extent of plane-wave source is infinite.
Since the radome of finite size cannot entirely encompass this
“infinitely sized” source, the equivalence theorem, which is
the basis of the PO and AI-SI methods, cannot be directly
used to achieve the excitation fields. Therefore, it is difficult
to apply existing methods to study the ARS properties in
receiving mode, especially for the large-size problems, since,
in this case, full-wave analyses are inefficient, while the use
of approximate or hybrid methods is problematic.
Recently, Wang et al. [1] proposed a hybrid integral
equation/ modified SI (MSI) method (called original IE/MSI
method hereafter in this paper) to analyze the performance
of ARS in receiving mode. This approach not only obviates
the previously stated deficiency of existing high frequency and
hybrid methods for ARS in receiving mode, but also reduces
memory requirement massively as compared to the purely
fast solvers accelerated full-wave solutions. However, as was
pointed out in [1], this method still has two drawbacks. The
first one is that it will become less accurate when the incidence
angle of plane wave with respect to the radome’s axis increases
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