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Int. J. Electron. Commun. (AEÜ)
journal homepage: www.elsevier.com/locate/aeue
Regular paper
Symmetric sum coarray based co-prime MIMO configuration for direction of
arrival estimation
☆
Junpeng Shi
a,b
, Guoping Hu
a,
⁎
, Xiaofei Zhang
b,
⁎
, Yu Xiao
a
a
Air and Missile Defense College, Air Force Engineering University, 710051 Xi’an, China
b
Electronic Information Engineering College, Nanjing University of Aeronautics and Astronautics, 210000 Nanjing, China
ARTICLE INFO
Keywords:
Co-prime multiple input multiple output
Direction of arrival estimation
Symmetric sum coarray
Degrees of freedom
ABSTRACT
This paper proposes a symmetric co-prime multiple input multiple output (MIMO) configuration for direction of
arrival (DOA) estimation, where the transmitter has
−M
sensors with spacing of N units and the receiver has
−N2
sensors with spacing of M units. By separating the transmitter and receiver into two subarrays respectively,
the symmetric sum coarray (SSC) exploits four sum coarrays based on the received signal model, and the dif-
ference coarray of SSC (DSSC) is developed by vectorizing the sample covariance matrix. The analytical ex-
pressions for the coarray aperture, the maximum consecutive integers and the attainable number of unique lags
are derived carefully. Compared with the existing configurations, SSC and DSSC can obtain larger number of
degrees of freedom (DOFs). Then, the DOA estimation of mutually coherent and uncorrelated targets is employed
for illustration. Simulation results demonstrate the effectiveness of proposed configuration.
1. Introduction
Recently, multiple input multiple output (MIMO) configuration has
been widely used for array signal processing and cellular communica-
tions [1], such as direction finding [2] and coordinated multipoint
(CoMP) techniques [3–5]. To be special, due to the high estimation
accuracy and resolution, direction of arrival (DOA) estimation has re-
ceived great attentions. Nevertheless, the conventional MIMO radars
mainly focus on the uniform linear arrays (ULAs) with inter-elements
spacing of less than or equal to half wavelength. In this case, if both the
transmitter and receiver are composed of N sensors, the upper bounds
of degrees of freedom (DOFs) for monostatic and bistatic MIMO radars
are
−N2
and
respectively.
To obtain larger DOFs, sparse array structures with MIMO radars
have been exploited from the coarray viewpoint. To be special, com-
pared with minimum redundancy array (MRA) [6,7] and nested array
[8], the co-prime array (CPA) [9,10] can avoid the complicated com-
putational search and also address the mutual coupling issue [11,12].In
[13], a novel co-prime array adaptive beamforming algorithm was
proposed for taking full advantage of co-prime property. The authors in
[14] generate a compressive sensing-based co-prime array for efficient
DOA estimation with increased DOFs. Besides, some latest off-grid
methods have also been proposed for DOA estimation with CPAs. Ref.
[15] proposed a covariance matrix reconstruction approach by
formulating a low-rank matrix reconstruction problem with nuclear
norm. In [16] , a perturbed sparse Bayesian learning (SBL) -based al-
gorithm was developed to solve the inherent limitation of the pre-
defined spatial discrete grids. In [17], SBL framework was developed
for wide-band DOA estimation with low complexity.
Recently, the co-prime MIMO radars have been proposed to increase
the DOFs using different array geometries [18–21]. Li et al. [18] em-
ployed the unitary ESPRIT to acquire the unique DOAs by finding the
common results from transmit and receive arrays. Based on the gen-
eralized difference co-array of the sum co-array (DCSC), a generalized
co-prime MIMO radar [19] was proposed to obtain more DOFs. The
authors in [20] applied the flexible CPA configuration on the trans-
mitter and receiver for resolving more targets. Besides Zheng et al. [21]
also exploited the joint DOA and direction of departure (DOD) esti-
mation for bistatic MIMO radars with CPA.
However, since the resulting coarray structure of co-prime MIMO
configuration contains more subarrays than the prototype CPAs in
[9,10],itisdifficult to obtain the precise analytical expressions of the
achievable DOFs. For example, the methods in [18,20,21] only present
the number of unique lags without theoretical derivation. Besides, most
of the aforementioned studies only focus on the vectorization of sample
covariance matrix and few have considered the coarray structure of the
received signals. Therefore, this paper considers the co-array structure
of the proposed co-prime MIMO configuration, where the symmetric
https://doi.org/10.1016/j.aeue.2018.07.022
Received 24 October 2017; Accepted 21 July 2018
☆
This work is supported by the National Natural Science Foundation of China (Grant Nos. 61601504, 61501504 and 61601167).
⁎
Corresponding authors.
E-mail addresses: hgp6068@163.com (G. Hu), zhangxiaofei@nuaa.edu.cn (X. Zhang).
Int. J. Electron. Commun. (AEÜ) 94 (2018) 339–347
1434-8411/ © 2018 Published by Elsevier GmbH.
T