干涉式L形阵的二维高精度方向估计

为了提高常规L形阵测角精度，结合干涉测量理论与常规L形阵波达方向估计技术，提出了以干涉式L形阵来实现阵列孔径扩展，提高测角精度的方法。由于干涉阵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。采用双尺度旋转不变子空间解模糊算法，以短基线得到的粗估计为参考，解长基线得到的精估计的模糊，从而得到高精度无模糊的方向估计。在分析干涉式L形阵的波达方向估计性能时，采用近似法计算方向余弦估计的均方根误差下界，同时分析了干涉阵的基线模糊门限与信噪比门限之间的关系。仿真结果验证了干涉式L形阵的有效性及方向估计的高精度性能。

High accuracy 2-D direction finding using interferometric-like L-shaped array

In order to improve the accuracy of direction finding with the conventional L-shaped array,an interferometric-like L-shaped array is proposed,which is based on the interferometry theory and the techniques of direction of arrival(DOA) estimation of conventional L-shaped array.The interferometric-like L-shaped array leads to aperture extension and higher accuracy of DOA estimation.The interferometric-like array with the baselines greater than a half-wavelength results in the grating lobes in the combined array beampattern and ambiguity in DOA estimation.A dual-size estimation of signal parameters via rotational invariance techniques(ESPRIT) based algorithm is used to resolve the ambiguities,where the short baseline yields unambiguous but high-variance direction cosine estimates to disambiguate low-variance but cyclically ambiguous estimates from the longer baseline,then lower variance and non-ambiguous estimates are achieved.The lower bound of mean square error of direction cosine is approximately calculated.The relation of the baseline ambiguity threshold and the signal to noise ratio threshold is analyzed.Simulation results demonstrate the effectiveness and high accuracy of this interferometric-like L-shaped array.