Comparative Study of Near-field ISAR and
MIMO Radar Images
Yongze Liu, Xiaojian Xu, and Xiaoyu He
School of Electronics and Information Engineering, Beihang University
37 Xueyuan Road, Beijing, 100191, China
Email: xiaojianxu@buaa.edu.cn
ABSTRACT
Inverse synthetic aperture radar (ISAR) imaging of turntable
targets has been widely used in radar cross section (RCS)
diagnosis. A major shortcoming is that the data acquisition time is
long due to the time-consuming mechanical rotation of a turntable.
The distinctive advantage of a multiple-input multiple-output
(MIMO) radar which is capable of imaging a target with high
resolution by using only one snapshot makes it more attractive. In
this paper, a comparative study is performed between near-field
ISAR and MIMO radar images. Tests are carried out on classical
objects such as metallic cylinder and trihedral corner reflector, as
well as an aircraft model.
CCS Concepts
• Hardware
Signal processing systems
Digital signal
processing.
Keywords
MIMO radar; ISAR; near-field imagery; scattering diagnosis.
1. INTRODUCTION
High resolution radar imaging of complex targets is useful for
diagnostic studies of target scattering mechanism. Among others,
inverse synthetic aperture radar (ISAR) [1][2] image of rotating
objects is widely used for such applications. It obtains high range-
resolution by emitting wideband signals and high cross-resolution
through the rotation of a turntable. A major shortcoming is that
the data acquisition time is long due to the mechanical rotation of
a turntable. Multiple-input multiple-output (MIMO) radar [3][4] is
an enabling technique capable of imaging target with high
resolution using only one snapshot, which makes it more
attractive to the researchers engaging in radar cross section (RCS)
measurement [5]. Each virtual element in MIMO array is
synthesized by a pair of transmit and receive elements.Therefore,
for near-field applications, virtual element cannot be considered
as an equivalent monostatic transmit/receive element. In this
paper, a comparative study is performed between near-field ISAR
and MIMO radar images.Tests are carried out onclassical objects
such as metallic cylinder and trihedral corner reflector, as well as
an aircraft model. Experimental results demonstrate that in most
cases where the major scattering mechanisms are not so sensitive
to small bistatic geometries, the near-field MIMO and ISAR
images have a good similarity for targets.
The remainder of this paper is organized as follows.Signal models
of ISAR and MIMO radar are introduced in section 2. Section 3
performs a comparative study of near-field ISAR and MIMO
radar and presents a series of experimental results with detailed
analysis. We conclude the paper in section 4.
2. ISAR AND MIMO RADAR SIGNAL
MODELS
2.1 ISAR Signal Model
Turntable ISAR imaging of targets is a monostatic measurement
where an antenna is used as transmit sensor as well as receive
sensor. The imaging aperture is obtained through the rotation of a
turntable. Therefore, the measured data are the monostatic RCS
data of targets.
ISAR signal model can be expressed as equation (1) and (2) [1][2]
0
4
()
( ,) (,)
f
j RR
c
s f f x y e dxdy
π
θ
−−
=
(1)
where
represents the scattered fields measured by receive
antenna,
is the radar frequency,
denotes the rotating
azimuth angle,
denotes the target scattering function,
is the target zone,
is the distance from the radar to the scatterer
at position
.
The constructed target scattering function can be represented as
0
m
m
4
()
2
2
ˆ
(,) ( ,)
e
s
f
j RR
f
c
f
f x y s f e dfd
π
θ
θ
θθ
−
−
=
∫∫
(2)
where
is the maximal range of rotating angle,
is the start
frequency,
is the stop frequency.
2.2 MIMO Array and Signal Model
MIMO radar employs a small number of antennas to configure a
sparse array which can synthesize a large virtual aperture and
provide higher degree of freedom. The configuration of the
MIMO array [4][6] used in this work is shown in Fig.1 (a). The
transmit elements consist of two groups of antennas placed at the
two ends of the array, while the receive elements are uniformly
located in the middle of the array. Suppose that the MIMO array
consists of
transmit elements and
receive elements, such
that
virtual elements are synthesized. The interspacing of
the transmit and the receive elements are set to be
and
,
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ICSPS' 17, November 27–30, 2017, AUT, Auckland, New Zealand.