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Clutter Nulling Performance of SMI in Amplitude
Heterogeneous Clutter En vironments
In order to investigate the clutter nulling performance of
the sample matrix inversion (SMI) algorithm in amplitude
heterogeneous environments, we derive an analytical expression
for the average signal-to-interference plus noise ratio (SINR) loss
based on random matrix theory. The results show that comparing
with the case where the training data utilizes the homogeneous
secondary samples (which are independent and identically
distributed (IID) to the snapshot in the cell under test (CUT)),
formulating the adaptive weight with the secondary samples
which have stronger clutter power than that in CUT will in crease
the output SINR. Nevertheless, the achievable performance
improvement might be quite limited. Conversely, selecting the
secondary samples with weaker clutter power will degrade the
performance.
I. INTRODUCTION
Space time adaptive processing (STAP) has been
recognized as a critical technique in airborne radar for
improving the detection performance of low-velocity
target [1, 2]. In STAP, a key problem is the estimation
of the interference covariance matrix and computation
of the adaptive weight (here interference means
clutter plus noise). Typically, the snapshots from
the neighborhood range bins, which are referred
to as secondary samples, are used to adaptively
formulate the interference covariance matrix. To
make a satisfactory estimation, it is required that the
secondary samples are homogenous, i.e., independent
and identically distributed (IID) to the snapshot in the
cell under test (CUT).
In the real world, however, such homogeneity
cannot always be achieved. Nonstationarity of the
external environment will lead to clutter heterogeneity,
i.e., the secondary samples do not share the same
statistics as those in CUT [3]. As a consequence
Manuscript received May 31, 2011; revised October 26, 2011 and
March 21, 2012; released for publication October 19, 2012.
IEEE Log No. T-AES/49/2/944544.
Refereeing of this contribution was handled by Y. Abramovich.
This work was supported in part by Anhui Provincial Natural
Science Foundation under Grant 1208085QF103, National Natural
Science Foundation of China under Grant 61171120 and 61201379,
the National High Technology Research and Development Program
(“863” Program) of China under Grant 2011AA8013019c, and the
Foundation of Tsinghua University under Grant 20101081772.
0018-9251/13/$26.00
c
° 2013 IEEE
1366 IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS VOL. 49, NO. 2 APRIL 2013