Transmit beamforming for DOA estimation based on Cramer–Rao bound optimization in subarray MIMO radar

International Journal of Antennas and Propagation

2021

By transmitting multiple independent waveforms at the transmit side and processing echoes of spatial targets at the receive side, Multiple Input Multiple Output (MIMO) radar enjoys virtual array aperture expansion and more degree of freedom (DOF), both of which favors the application of direction finding or estimation of direction of arrival (DOA). The expanded virtual aperture provides higher angular resolution which also promotes the precision of DOA estimation, and the extra DOF brought by waveform diversity can be leveraged to focus energy in certain spatial region for better direction-finding capacity. However, beamspace methods which match certain beampatterns suffer from deteriorated performance and complexity in implementation, and the advantage of virtual array aperture is limited by its virtual element redundancy. As an important performance indicator of DOA estimation, Cramer–Rao Bound (CRB) is closely connected to the array configuration of the system. To reduce the complexity of the system and improve CRB performance at the same time, in this paper, the virtual array of MIMO radar is designed directly by selecting outputs from matched filters at the receive side. For the sake of fair comparison, both scenarios with and without priori directions are considered to obtain optimized virtual array configuration, respectively. The original combinatorial problems are approximated by sequential convex approximations methods which produce solutions with efficiency. Numerical results demonstrate that the proposed method can provide thinned virtual arrays with excellent CRB performance.

Section: Introductionmentioning

confidence: 99%

Thinned Virtual Array for Cramer Rao Bound Optimization in MIMO Radar

International Journal of Antennas and Propagation

2021

“…In fact, Tang et al. [21] shows that partially correlated waveforms in the space are equivalent to those formed by transmitting orthogonal ones from multiple subarrays through the proper design of a beamforming matrix, which suggests that an array partition based on a beamforming matrix provides more DOFs than directly designing array structures. In this way, cross‐correlation between different waveforms, the coherence of an array manifold matrix, the partition of subarrays and beamforming matrix, and selection of a suitable target of optimization are crucial.…”

Section: Introductionmentioning

confidence: 99%

Coherence optimised subarray partition for hybrid MIMO phased array radar

IET Microwaves Antenna & Prop

2021

Hybrid MIMO phased array radar (HMPAR) is widely recognized in the research of radar systems owing to its capacity to provide a balance or trade-off between transmit coherent gain and waveform diversity gain. The balance or trade-off between these two gains is closely related to spatial coherence between different arrays, represented by the degree of cross-correlation between steering vectors over different angles. Proper subarray partitions can provide an extra degree of freedom for optimising the coherence of the array manifold. A coherence optimised subarray partition for HMPAR is proposed with an analysis of connections between coherence and subarray partitions. First, the definition of coherence of array manifold is presented, and its connection between beampattern and the signal to interference plus noise ratio (SINR) is analysed. Next, the problem of optimising array manifold coherence is transformed into the discrete coherence optimization of the steering vector codebook. By properly selecting different codewords with the proper degree of correlation between each other, coherence between the target and interference steering vectors is optimised. The original combinatorial problem is approximated by a series of subproblems, which is solved in iteratively. Numerical results revealed that the proposed subarray partition provides lower coherence, lower beampattern peak sidelobes and higher SINR compared with`other subarray configurations.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

“…In contrast, formulating overlapped subarrays with each one transmitting an orthogonal waveform reduces the complexity on both hardware and computation of waveforms, which is the basic idea behind Phased MIMO radar. It is proven in [8] and [17], [18] that partially correlated waveforms are equivalent to orthogonal ones transmitted from array with certain subarray configurations. In addition, appropriate subarray partitions have more potential of providing spatial degree of freedom(DOF) for achieving trade-off than waveform design does, since subarray partitions may further expand virtual aperture, which is helpful for interference mitigation [19].…”

Section: Introductionmentioning

confidence: 99%

Hybrid MIMO Phased Array Radar With Center-Spanned Subarrays

2019

IEEE Access

Hybrid Multiple-Input-Multiple-Output(MIMO) phased array radar, or Phased MIMO radar, is recognized for its capacity to provide trade-off between transmit coherent gain and waveform diversity gain. Such trade-off can be flexibly implemented by changing subarray partition schemes of the system, which in turn enhances system performance. In this paper, a center-spanned subarray configuration is proposed with detailed steps to develop: First, the center element of the whole transmit array is chosen. Next, the surrounding region of center element is determined as the center subarray for subsequent spanning. Finally, the subarray partition is implemented through spanning subarrays around the center subarray. Both theoretical derivations and simulation results reveal that the hybrid MIMO phased array radar with the proposed center-spanned subarray configuration has lower sidelobe beampattern and higher Signal to Interference Noise Ratio(SINR) than that of equally or unequally overlapped subarray partitions. INDEX TERMS Beampattern, center-spanned sub-arrays, phased MIMO radar, SINR.