TOEPLITZ MATRIX-BASED TRANSMIT COVARIANCE MATRIX OF COLOCATED
MIMO RADAR WAVEFORMS FOR SINR MAXIMIZATION
Wei Xiong
1
, Maria Greco
2
, Fulvio Gini
2
, Gong Zhang
1
, Zhenni Peng
3
1 Key Laboratory of Radar Imaging and Microwave Photonics, Ministry of Education, Nanjing
University of Aeronautics and Astronautics, Nanjing 211106, China
2 Dipartimento di Ingegneria dell’ Informazione, University of Pisa, Pisa 56122, Italy
3 Key Laboratory of Advanced Technology for Small and Medium-sized UAV, Ministry of Industry and
Information Technology, Nanjing 210016, China
Emails: wxiong_nuaa@sina.com; m.greco@iet.unipi.it; f.gini@ing.unipi.it; gzhang@nuaa.edu.cn
ABSTRACT
Focusing on the signal-to interference-plus-noise ratio
(SINR) maximization in colocated multiple-input multiple-
output (MIMO) radars, using the covariance matrix design
of transmitted waveforms, we propose a kind of transmit
covariance matrix (TCM)
with the form of symmetrical
Toeplitz matrix, whose full rank characteristic firstly can
sufficiently exploit the waveform diversity advantage of
MIMO radar to further suppress the maximum number of
interfering sources. Meanwhile, the positive semi-definition
characteristic of
guarantees that these TCMs
can be synthesized with binary phase shift keying (BPSK)
waveforms in closed form. Furthermore, employing certain
proposed TCM, higher SINR level can be yielded, and
lower sidelobe levels (SLLs) can be obtained for the
unwanted sidelobe interference suppression. Simulation
results validate the better performance of our proposed
TCMs in comparison with the phased array, omnidirectional
MIMO radar and the recently proposed TCMs.
Index Terms—colocated MIMO radar, transmit
covariance matrix, Toeplitz matrix, SINR maximization
1. INTRODUCTION
For the multiple-input multiple-output (MIMO) radar,
waveform design always is one of the most important issues
[1-14], which generally can be classified into the direct or
indirect methods. In the direct design approaches [1-6], the
transmitted signal symbols are directly calculated and some
W. Xiong’s work was supported by the National Natural Science
Foundation of China under grants 61471191, 61501233, 61671241 and
61501228, Aeronautical Science Foundation of China under grant
20152052026, the Funding of Jiangsu Innovation Program for Graduate
Education under grant KYZZ16_0169, the Fundamental Research Funds
for the Central University under grant 3082017NP2017421, the Base
Research Foundation under grant NS2015040 and also funded by the
Natural Science Foundation of Jiangsu under grant BK20140825 .
special waveform characteristics must be considered to be
satisfied, such as orthogonality, low peak-to-average power
ratio, constant modulus, similarity constraints and so on [6].
However, due to the flexibility and lower system design
complexity, the indirect MIMO waveform design has
recently received much attention [7-13], where the transmit
covariance matrix (TCM) R of the transmitted signals is
first designed, and then the transmitted waveform symbols
are generated. As shown in [7][8], for a given positive semi-
definite R, binary phase shift keying (BPSK) waveforms
can be synthesized to realize R in closed form. Focusing on
the TCM-based waveform design, some methods have been
proposed [9-13]. In [9], a TCM R
2x
using a cosine Toeplitz
matrix is presented and yield gains in SINR level. Though
the sidelobe levels (SLLs) of receive beampattern using R
2x
are lower, the rank of R
2x
is only 2, that is, the most
important degree of freedom (DOF) advantage cannot be
exploited for the interference suppression. Moreover,
is not positive semi-definite [9][10], which
cannot guarantee to synthesize R
2x
with BPSK in closed
form. Considering the full-rank constraint of R and positive
semi-definition of
are proposed as TCMs to achieve higher SINR
levels in [10], however, the full rank property of these two
TCMs is not proofed rigorously and the achieved SINR is
not the optimum with the prior knowledge of locations.
In this paper, we have extended the two matrices in [10]
to a kind of more general symmetrical Toeplitz matrix
is the control
parameter and
denotes the number of transmit
antennas. It is demonstrated that
is also positive semi-definite. Moreover,
the
with smaller m yields higher SINR level, and even
gets closed to the one of phased array. While the
with
certain larger m (e.g. m =1.5 or 2) could obtain the receive
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