针对互耦效应下相干信源的波达方向(direction of arrival,DOA)估计问题,提出一种基于阵列接收数据一阶统计量的解相干及互耦自校正算法.算法利用阵元接收数据的一阶统计量构造伪协方差矩阵,理论推导证明,互耦系数已从理想导向矢量中剥...针对互耦效应下相干信源的波达方向(direction of arrival,DOA)估计问题,提出一种基于阵列接收数据一阶统计量的解相干及互耦自校正算法.算法利用阵元接收数据的一阶统计量构造伪协方差矩阵,理论推导证明,互耦系数已从理想导向矢量中剥离,且该矩阵的秩与信源相关性无关,仅与信源个数相等,即实现了信源的解相干及互耦自校正,因此通过对重构矩阵进行一次特征分解即可实现DOA估计.此外,对算法的子空间估计性能及由互耦系数导致的测角模糊性进行了分析,结果表明该算法实现过程简单,计算量小,在低信噪比和短快拍数时仍具有很高的估计性能.仿真结果验证了算法的有效性.展开更多
From Helmholtz equation of the harmonic electromagnetic waves, the integral equations of the light field at the medium boundaries are obtained by use of the Green's theorem and are discretized into linear equation...From Helmholtz equation of the harmonic electromagnetic waves, the integral equations of the light field at the medium boundaries are obtained by use of the Green's theorem and are discretized into linear equation set with the values of the light field and its derivative as the unknowns. On solving the linear equation set, we realize the rigorous computations of the light fields at the boundaries. Then the intensities of the light waves scattered by the random self-affine fractal surfaces in the optical near-field are calculated, and the propagation characteristics, the evolutions of the contrast and the intensity probability density function of the near-field speckles are studied in detail. The near-field speckles are much different from the conventional speckles in the diffraction regions and in the imaging systems. There are obvious local fluctuations in the intensity distributions of the near-field speckles and such fluctuations disappear after propagating a distance of one wavelength from the medium surfaces. For the random surfaces with smaller lateral correlation lengths, the speckle contrasts approach the saturation values and the speckle fields approach Gaussian distribution within the near-field, while for the random surfaces with larger lateral correlation lengths, such evolutions become comparatively slow.展开更多
针对低信噪比和少快拍数情况下相干信源二维波达方向(direction of arrival,DOA)估计精度大幅下降的问题,提出了基于一阶统计量的子空间旋转不变(ESPRIT)解相干算法。该算法首先对阵元接收数据进行求均值运算,利用每个阵元接收数据的一...针对低信噪比和少快拍数情况下相干信源二维波达方向(direction of arrival,DOA)估计精度大幅下降的问题,提出了基于一阶统计量的子空间旋转不变(ESPRIT)解相干算法。该算法首先对阵元接收数据进行求均值运算,利用每个阵元接收数据的一阶统计量构造三个Toeplitz形式伪协方差矩阵,实现相干信源的解相干;然后构造一个扩展协方差矩阵并对其进行一次奇异值分解即可实现相干信源的二维DOA估计。仿真结果表明:该算法在低信噪比和少快拍数下的估计性能优于空域平滑波达方向矩阵法,估计精度高,且避免了传统算法对信号协方差矩阵的处理过程,计算复杂度低,实时性高。展开更多
文摘针对互耦效应下相干信源的波达方向(direction of arrival,DOA)估计问题,提出一种基于阵列接收数据一阶统计量的解相干及互耦自校正算法.算法利用阵元接收数据的一阶统计量构造伪协方差矩阵,理论推导证明,互耦系数已从理想导向矢量中剥离,且该矩阵的秩与信源相关性无关,仅与信源个数相等,即实现了信源的解相干及互耦自校正,因此通过对重构矩阵进行一次特征分解即可实现DOA估计.此外,对算法的子空间估计性能及由互耦系数导致的测角模糊性进行了分析,结果表明该算法实现过程简单,计算量小,在低信噪比和短快拍数时仍具有很高的估计性能.仿真结果验证了算法的有效性.
基金sponsored by the National Natural Science Foundation of China(Grant No.69978012)by the National Key Basic Research Special Foundation(NKBRSF)of China(Grant No.G1999075200).
文摘From Helmholtz equation of the harmonic electromagnetic waves, the integral equations of the light field at the medium boundaries are obtained by use of the Green's theorem and are discretized into linear equation set with the values of the light field and its derivative as the unknowns. On solving the linear equation set, we realize the rigorous computations of the light fields at the boundaries. Then the intensities of the light waves scattered by the random self-affine fractal surfaces in the optical near-field are calculated, and the propagation characteristics, the evolutions of the contrast and the intensity probability density function of the near-field speckles are studied in detail. The near-field speckles are much different from the conventional speckles in the diffraction regions and in the imaging systems. There are obvious local fluctuations in the intensity distributions of the near-field speckles and such fluctuations disappear after propagating a distance of one wavelength from the medium surfaces. For the random surfaces with smaller lateral correlation lengths, the speckle contrasts approach the saturation values and the speckle fields approach Gaussian distribution within the near-field, while for the random surfaces with larger lateral correlation lengths, such evolutions become comparatively slow.
文摘针对低信噪比和少快拍数情况下相干信源二维波达方向(direction of arrival,DOA)估计精度大幅下降的问题,提出了基于一阶统计量的子空间旋转不变(ESPRIT)解相干算法。该算法首先对阵元接收数据进行求均值运算,利用每个阵元接收数据的一阶统计量构造三个Toeplitz形式伪协方差矩阵,实现相干信源的解相干;然后构造一个扩展协方差矩阵并对其进行一次奇异值分解即可实现相干信源的二维DOA估计。仿真结果表明:该算法在低信噪比和少快拍数下的估计性能优于空域平滑波达方向矩阵法,估计精度高,且避免了传统算法对信号协方差矩阵的处理过程,计算复杂度低,实时性高。
