ANOVELMONOSTATICSARHRWSIMAGINGSCHEME
FORMARITIMESURVEILLANCE
JiachengNi
1
,QunZhang
1,2
,KaiWang
1
,FuFeiGu
1
,YingLuo
1
1
Air Force Engineering University, Institute of Information and Navigation, Xi’an, China
2
Fudan University, Key Laboratory for Information Science of Electromagnetic Waves (Ministry of
Education), Shanghai, China
ABSTRACT
This paper focuses on the problem of maritime surveillance
for ship detection and proposes a novel monostatic SAR
high resolution wide swath imaging scheme. The scheme
changes the way that Scan SAR illuminates sub-scenes, and
proposes a scanning mode using the prior information of
ships’ spatial distribution in each sub-scene. Firstly, a
method based on range profiles is used to obtain the target
number in each sub-scene. After that, the radar illuminates
each sub-scene in a probability calculated by a transfer-
probability matrix. Finally, a compress sensing algorithm is
utilized to reconstruct each sub-scene using the obtained
sparse aperture echo data, and the whole wide swath image
is joint by putting all the sub-scenes together. Experimental
results show that the proposed imaging scheme can get a
wide swath image effectively without reducing the image
resolution.
Index Terms— SAR imaging, Compressed Sensing,
Range profile, transfer-probability matrix.
1.INTR ODUCTION
Conventional monostatic synthetic aperture radar (SAR)
systems are not capable of fulfilling the increasing demands
of improved imaging resolution and wider swath coverage,
especially in applications such as surface monitoring and
maritime surveillance. Accordingly, many techniques have
been proposed. An excellent overview and performance
comparison is given in [1] and [2].The emerging HRWS
imaging literature can be summarized as two categories. The
first category is schemes of multiple-input and multiple-
output (MIMO) SAR-based solution. MIMO SAR can
provide additional processing freedom degrees, but it has
the drawbacks of further increased data amount and
significantly complicated hardware at the same time. The
second category is a particular SAR system solution called
Scan SAR. Scan SAR can achieve wide swath coverage at
the cost of severe azimuth resolution loss, as the length of
each burst in Scan SAR is usually short [3][4].
Recently, SAR imaging based on compressed sensing
(CS) has attracted much attention [5][6]. Researches have
shown that CS theory can lead to significant coverage or
resolution improvement in Scan SAR systems. In [7],
random steering along the azimuth direction is used to
increase the resolution. In [8], CS theory is utilized to
perform azimuth imaging using a sparse aperture. However,
all these works use uniformity scanning mode to illuminate
each sub-scenes in the same probability. This scanning
method may cause a severe beam resources loss when
facing a maritime surveillance task. Since a ship target is
much smaller than the background in the imaging scene, one
sub-scene may have no ship while another may contain
several ships. Therefore, it is obviously unwise that these
two sub-scenes share the same scanning beams.
In this paper, we extend and generalize a new imaging
scheme of scan mode SAR based on CS, in the case of
bright ship targets over a dark sea background. We show
that this new imaging method can not only multiply the
imaging coverage but also maintain its azimuth resolution
compared to other CS-based Scan mode SAR. The main
idea of the proposed imaging scheme lies in the fact that in a
maritime surveillance task, if a sub-scene contains a larger
number of ships, it usually needs higher imaging accuracy.
So our purpose is to allocate the radar beam resources
properly according to the principle that let the scene that has
the largest number of ships gains the highest radar
illuminating probability.
This paper is organized as follows. In Section II, the
model of the proposed imaging scheme is introduced. In
Section III, the new scanning mode is presented and detailed.
In Section IV, some simulations are presented to show the
effectiveness of the proposed scheme. Section V provides
the conclusion.
2.MODELOFTHEPROPOSEDSCHEME
The model of the proposed imaging scheme is shown in Fig
1. In the proposed scheme each sub-scene is fully covered
by a single radar beam, which allows the beam to illuminate
each sub-scene in a particular probability and ensures the
radar beams synthesize a sparse aperture to reconstruct high
resolution images using CS-based methods. As can be seen
in Fig 1, the proposed scheme contains two parts: the
scanning mode and the pointing mode. First, radar uses the
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