共轭对称约束差分恒模波束形成方法

传统的恒模波束形成算法在期望信号的信噪比较低的情况下容易误收敛到干扰信号，导致波束形成算法失效。针对上述问题，本文提出了一种共轭对称约束差分恒模算法。该算法首先引入了一种新的差分恒模代价函数，然后根据均匀直线阵列导向矢量的特殊结构，推导出了共轭对称约束条件。最后通过对数据进行归一化处理，使得步长因子的选择独立于输入信号功率，降低了步长因子的选取难度，提高了算法的实用性。仿真实验表明，本文算法在低信噪比下仍然保持了良好的收敛性能，并且对阵列幅相误差和初始权重矢量的误差也具有较强的稳健性。 

Conjugate Symmetric Constraint Differential Constant Modulus Beamforming Algorithm

Conventional constant modulus beamforming algorithms (CMA) may converge to interference with high probability when signal-to-noise ratio (SNR) of desired signal is low, which would result in severe performance degradation of beamforming methods. In order to above problem, a conjugate symmetry constraints differential CMA (CSC-DCMA) is proposed in this paper. Firstly, the algorithm introduces a novel differential constant modulus cost function. Then according to the special structure of the steering vector of uniform linear array, a conjugate symmetry constraint is given out. Finally, by normalizing input data, the selection of step factor is independent of the input signal power. As a result, the difficulty of selecting step factor is relieved and practicability of the proposed algorithm is improved. Simulation results show that the proposed algorithm is able to maintain good convergence performance at low SNR. Also, the robustness against initial weight vector error and sensor gain and phase error is verified.