基于root-RARE算法的非同构分布式阵列高精度方向估计

针对非同构分布式阵列无法使用旋转不变子空间算法(estimation of signal parameters via rotation invariant technique algorithm, ESPRIT)，同时为了提高非同构分布式阵列的角度估计精度，提出基于求根降秩算法(root rank reduction estimator, root-RARE)的目标波达方向估计方法。由于分布式阵列的基线长度远大于半波长，合成方向图出现栅瓣，导致测角模糊。算法以root-RARE与多重信号分类算法(multiple signal classification, MUSIC)联合解模糊，以root-RARE得到的粗估计为参考，解整个非同构分布式阵列MUSIC谱估计的模糊，从而得到高精度无模糊的估计。推导非同构分布式阵列方向估计的克拉美罗界，分析算法的波达方向估计性能，同时分析分布式阵列方向估计时的基线模糊门限与信噪比门限之间的关系。仿真结果验证所提算法方向估计的正确性及有效性。

High accuracy direction finding based on root-RARE using distributed non-identical subarray antenna

In order to improve the accuracy of direction finding of distributed non-identical subarray antenna radar which cannot apply the estimation of signal parameters via the rotation invariant technique algorithm (ESPRIT), a new method based on root rank reduction estimator (root-RARE) is proposed for estimating the direction of arrival (DOA) of the target. The length of the distributed subarray antenna baselines is longer than the half wavelength, which results in grating lobes in the combined array beampattern and ambiguity in DOA estimation. An estimation of signal parameters via the combination of the root-RARE and multiple signal classification (MUSIC) is used to resolve the ambiguities. The root-RARE yields unambiguous but high variance direction estimates to disambiguate low variance but cyclically ambiguous estimates from the MUSIC algorithm with the whole distributed subarray antennas, then lower variance and non-ambiguous estimates are achieved. The Cramer-Rao bound of direction is calculated. The performance of DOA estimation and the relation between the baseline ambiguity threshold and the signal to noise ratio threshold are analyzed. Simulation results demonstrate the validity and effectiveness of the proposed algorithm.