Joint estimation of DOA, frequency, and polarization based on cumulants and UCA

A joint estimation algorithm of direction of arrival （DOA）, frequency, and polarization, based on fourth-order cumulants and uniform circular array （UCA） of trimmed vector sensors is presented for narrowband non-Gaussian signals. The proposed approach, which is suitable for applications in arbitrary Gaussian noise environments, gives a closed-form representation of the estimated parameters, without spectral peak searching. An efficient method is also provided for elimination of cyclic phase ambiguities. Simulations are presented to show the performance of the algorithm.

Resolution performance analysis of cumulants-based rank reduction estimator in presence of unexpected modeling errors

Compared to the rank reduction estimator （RARE） based on second-order statistics （called SOS-RARE）, the RARE employing fourth-order cumulants （referred to as FOC-RARE） is capable of dealing with more sources and mitigating the negative influences of the Gaussian colored noise. However, in the presence of unexpected modeling errors, the resolution behavior of the FOC-RARE also deteriorate significantly as SOS-RARE, even for a known array covariance matrix. For this reason, the angle resolution capability of the FOC-RARE was theoretically analyzed. Firstly, the explicit formula for the mathematical expectation of the FOC-RARE spatial spectrum was derived through the second-order perturbation analysis method. Then, with the assumption that the unexpected modeling errors were drawn from complex circular Gaussian distribution, the theoretical formulas for the angle resolution probability of the FOC-RARE were presented. Numerical experiments validate our analytical results and demonstrate that the FOC-RARE has higher robustness to the unexpected modeling en＇ors than that of the SOS-RARE from the resolution point of view.

Performance of cumulant-based rank reduction estimator in presence of unexpected modeling errors

Compared with the rank reduction estimator(RARE) based on second-order statistics(called SOS-RARE), the RARE based on fourth-order cumulants(referred to as FOC-RARE) can handle more sources and restrain the negative impacts of the Gaussian colored noise. However, the unexpected modeling errors appearing in practice are known to significantly degrade the performance of the RARE. Therefore, the direction-of-arrival(DOA) estimation performance of the FOC-RARE is quantitatively derived. The explicit expression for direction-finding(DF) error is derived via the first-order perturbation analysis, and then the theoretical formula for the mean square error(MSE) is given. Simulation results demonstrate the validation of the theoretical analysis and reveal that the FOC-RARE is more robust to the unexpected modeling errors than the SOS-RARE.

Joint frequency, 2D AOA and polarization estimation using fourth-order cumulants

Based on fourth-order cumulant and ESPRIT algorithm, a novel joint frequency, two-dimensional angle of arrival (2D AOA) and the polarization estimation method of incoming multiple independent spatial narrow-band non-Gaussian signals in arbitrary Gaussian noise environment are proposed . The array is composed of crossed dipoles parallel to the coordinate axes. The crossed dipole positions are arbitrarily distributed. Computer simulation confirms its feasibility.

Array gain of fourth-order cumulants beamforming under typical probability density background

The fourth-order cumulant of zero mean Gaussian distribution noise always equals to zero theoretically. In practice the probability density of noise and reverberation is the key problem to performance of the fourth-order cumulant beamforming technique. In this paper, the array gain functions of the fourth-order cumulant beamforming are deducted considering the instantaneous amplitude distribution of the ambient sea noise and bottom reverberation respectively. And the relationships are determined between array gain and the factors including the number of the array elements, the fourth-order and second-order statistical properties of the noise and reverberation, and the input signal-to-noise ratio. It is also verified that there is a critical signal-to-interference ratio and the fourth-order cumulant beamforming can obtain higher gain and resolution than the conventional beamforming method when the ratio is larger than it. The results of experiment data processing demonstrate that the gain and the resolution of the fourth-order cumulant beamforming coincide with the theoretic.

色噪声下双基地MIMO雷达DOD和DOA联合估计

针对双基地多输入多输出(multiple-input multiple-output,MIMO)雷达在色噪声环境中的收发角度估计问题,提出了一种基于改进四阶累积量的角度估计算法。该算法首先构造回波信号的四阶累积量矩阵,然后根据四阶累积量矩阵的形成规律,在保证虚拟阵列孔径有效扩展的前提下去除其中的冗余项,达到矩阵降维的目的。最后将降维后的矩阵特征分解得到噪声子空间,再利用四阶累积量的多重信号分类(multiple signal classification,MUSIC)算法实现最终的收发角度估计。所提算法不仅可以有效抑制高斯色噪声,并且能够减小四阶累积量矩阵的维数,降低计算的复杂度,仿真结果验证了该算法的有效性。

基于四阶累积量状态空间模型的间谐波参数估计

推导了间谐波的四阶累积量的对角切片,包含了准确的间谐波频率、幅度及相移信息。在四阶累积量的基础上,提出了一种基于状态空间模型的谐波参数估计方法,该方法实现了间谐波频率、幅度和相位的联合估计。仿真结果表明,所提方法能有效地抑制高斯色噪声,具有优越的参数估计性能。

基于四阶累积量相关信号的DOA估计

目的针对相干信号,在高斯色噪声的背景下,有效地进行信号的DOA估计。方法应用四阶累积量和修正MUSIC算法。结果二阶矩算法性能严重失效,累计量算法DOA估计性能好。结论利用四阶累积量和修正MUSIC算法相结合,在高斯色噪声的背景下具有良好的统计性能,是实现相干信号高分辨方位估计的有效方法。

基于TD-SCDMA无线定位虚拟线阵四阶累量修正MUSIC算法的研究

无线定位的圆-角定位技术中,DOA估计极其重要。本文针对基于TD-SCDMA智能天线预处理后的虚拟均匀线阵MUSIC算法带来的阵列孔径小,抗阵元误差扰动性差的不足,研究了基于模式空间虚拟均匀线阵四阶累量的MUSIC算法,由于虚拟线阵四阶累量MUSIC算法的应用范围局限于独立的信号源的DOA估计,不能用于相关信号源DOA估计,因而提出了基于模式空间虚拟均匀线阵四阶累量的修正MUSIC(FOC-MMUSIC)算法,有效地拓展了阵元孔径,改善了系统抗阵元误差扰动和算法对相关信号源DOA的估计性能。

基于四阶累积量自适应时延估计的改进

时间延迟估计在雷达和声纳等方面有着广泛的应用。为了在空间相关或不相关的高斯背景噪声下获得比较精确的时延估计值,提出了一种基于四阶累积量、借助于ETDE(Explicit Time Delay Estimation,利用sinc函数采样FIR滤波器)算法的自适应时延估计算法。此方法可以抑制相关或不相关高斯噪声的影响,可以跟踪时延,从而保证时延的唯一性,进而得到信号准确的时延估计。该算法在较低信噪比下能得到非高斯信号较准确的时延估计。理论分析和仿真结果证明了算法的有效性。

虚拟波束四阶累积量DOA估计方法

为满足复杂干扰场景和阵列误差因素影响下雷达微弱目标信号精确测向需求,提出一种基于均匀线阵构建虚拟波束,替代阵列接收信号进行四阶累积量(fourth-order cumulant,FOC)波达方向(direction of arrival,DOA)估计的算法。该算法包括两个关键步骤:一是利用阵列接收信号特征分解的方法,对信号主信息分量进行提取,并以构建的虚拟波束为输入,计算FOC矩阵;二是针对主分量虚拟波束波瓣外的起伏,利用高斯窗修正波束方向图的方法,进一步提升空间谱函数的估计精度。仿真结果表明,该方法在存在阵列误差的非理想因素下,对复杂电磁干扰场景下的目标信号DOA估计精度较现有FOC方法提高150%以上,尤其对于场内同时存在多个非等功率源信号时,所提方法对低信噪比目标DOA估计精度提升效果优势明显,对复杂干扰环境下DOA估计精度更高、适应性更强。

Hierarchical space–time block codes signals classification using higher order cumulants

An efficient method for blind classification of space time block codes （STBCs） based on fourth-order cumulants is proposed for a single receiver antenna. This paper presents a model of received STBCs signals in multiple input single output （MISO） communication systems and applies the characteristics of coding matrices to derive analytical expressions for the fourth-order cumu- lants to be used as the basis of an algorithm. The fourth-order cumulants at various delay vectors present non-null values that depend on the transmitted STBCs. Tests of nullity are accomplished by hypothesis testing. The proposed algorithm avoids the need for a priori information of modulation scheme, channel coefficients, and noise power. Consequently, it is well suited for non-cooperative scenarios. Simulations show that this method performs well even at low signal-to-noise ratios （SNRs）.

An Array Extension Method in a Noisy Environment

An array extension method in a noisy environment was proposed to improve angular resolution and array gain. The proposed method combines the FOC （fourth-order cumulants） technique with the ETAM （extended towed array measurements） method to extend array aperture and suppress Gaussian noise, First, successive measurements of a virtual uniform linear array were constructed by applying lburth-order cumulants to measurements of uniform linear array; Gaussian noise in these measurements was also eliminated. Then, the array was extended by compensating phase differences using the ETAM method, Finally, the synthetic aperture was extended further by the fourth-order cumulants technique. The proposed FOC-ETAM-FOC method not only improves angular resolution and array gain, but also effectively suppresses Gaussian noise. Furthermore, it inherits the advantages of the ETAM method. Simulation results showed that the FOC-ETAM-FOC method achieved better angular resolution and array gain than the ETAM method. Furthermore this method outperforms the ETAM method in Gaussian noise environment.

JOINTLY ESTIMATING BOTH RANGE AND DOA OF NEAR FIELD SOURCE

A computationally efficient method for jointly estimating both Directions Of Arrival (DOA) and ranges of near field sources is presented. The proposed algorithm does not need any spectral peak searching and the 2-D parameters are automatically paired. It is suitable for arbitrary additive Gaussian noise environment. Furthermore, its performances are confirmed by computer simulations.

Estimation method of DOA for DS-UWB signal

Direction of arrival(DOA)estimation is one of the key technologies in smart antennas in the direct sequence ultra wideband(DS-UWB)system.Traditional DOA estimation methods based on narrow-band signals are not suitable for such system.Therefore,a fourth-order cumulant-based estimation method of DOA for DS-UWB signal is proposed.This method is set on the frequency domain model of DS-UWB array signal.Simulation results show that the algorithm is effective and can guarantee adequate estimation accuracy.