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Sub-arrayed multiple-input multiple-output (MIMO) radar holds the benefits of waveform diversity and coherent processing gain jointly. Based on prior knowledge, we exploit the sub-arrayed MIMO radar to form multiple beams in the desired directions and null the power toward the interference or clutter. Meanwhile, to maximize the radiation efficiency of nonlinear amplifiers in radar systems, the transmit weight vectors are required to have constant modulus properties, which leads to a complicated nonconvex problem. To that end, an iteration method with high calculation efficiency based on the alternating direction penalty method (ADPM) framework is presented to resolve this problem. The original problem is transformed into a general bi-convex problem with bi-affine constraints via introducing auxiliary variables. A high convergence rate can be achieved by selectively increasing the penalty parameters in each iteration. For any initialization, the ADPM-based method is proved to converge. And the obtained convergent solution fulfills the Karush-Kuhn-Tucker (KKT) conditions. Finally, the effectiveness of the proposed method is demonstrated by simulation results. • The subarray structure can flexibly adjust the transmit gain of each beam. • Coherent processing gain can be achieved by designing the weight vector. • An ADPM-based algorithm is proposed to design the transmit beampattern. [ABSTRACT FROM AUTHOR]

In this paper, a two-dimensional (2D) direction of arrival (DOA) estimation algorithm by a large-space T-shaped array is proposed. The used T-shaped array consists of a generalized unfolded co-prime array and a symmetrically unfolded co-prime array. The minimum element space (MES) of the proposed T-shaped array can exceed half-wavelength of received signals. The symmetry of the T-shaped array is used to construct an extended cross-covariance matrix, singular value decomposition (SVD) of which can obtain multiple signal subspaces. By combining the co-prime characteristic of element spacing with the rotational invariance of uniform linear array, three extended signal subspaces can be obtained without using virtual elements. Using the three extended signal subspaces, high-precision 2D DOA estimation can be got. The proposed T-shaped array has strong robustness to mutual coupling. The proposed method can eliminate angle ambiguity caused by large-space and has higher estimation precision than many similar 2D DOA estimation algorithms. Many simulation results can prove the performance of the proposed scheme. [ABSTRACT FROM AUTHOR]

In this paper, a high-precision two-dimensional (2D) direction of arrival (DOA) estimation algorithm by three parallel uniform linear arrays (ULAs) is proposed. Both the internal spacing of each sub-array and the spacing between two adjacent sub-arrays can exceed the half-wavelength of incident signal. An extended propagator method (PM) algorithm is introduced to obtain a multiple extended propagator matrix by processing the covariance matrix of received signals. Then, by using the extended propagator matrix, unambiguous and high-precision 2D DOA estimation can be obtained without extra pairing process. For the proposed array construction, mutual coupling effect can be ignored as long as the element interval is large enough. The extended PM algorithm based on the proposed array has far higher precision than the existing similar algorithms, which can be proved by some simulation experiments. [ABSTRACT FROM AUTHOR]