多孔径接收机中数字相干合成效率统计模型

Statistical Model of Digital Coherent Combining Efficiency in Multi-aperture Receivers

为了减小大气湍流对自由空间光(FSO)通信系统的性能衰落,文章提出了基于数字相干合成的多孔径接收方案。数字相干合成技术依靠数字相位对齐算法将不同版本的信号进行相位对齐。通过考虑每个接收孔径的相位对齐误差,推导出多孔径空间光接收机中数字相位对齐合成效率的统计模型,其可以通过Satterthwaite方法近似表示为卡方分布的线性函数。基于该统计模型,推导出合成效率的均值、方差和概率密度函数的精确表达式。仿真结果表明,该模型在不同孔径和信噪比组合方案下是有效的。文章还利用该模型比较了孔径选择系统的通信性能,所提方法在强湍流下的性能优于等增益合并(EGC)全孔径合成方案。

In order to mitigate the performance fading of Free-Space Optical(FSO)communication system caused by atmospheric turbulence,a multi-aperture receiving scheme based on digital coherent beam combining is used.Digital coherent beam combining relies on the digital phase alignment algorithm to align the different versions of signals in phase.In this paper,the statistical model of combining efficiency for digital phase alignment is derived in multi-aperture FSO receivers by considering the phase alignment errors at each receiving aperture.It can be expressed as a linear function of chi-square distribution by Satterthwaite approximation.Based on this statistical model,we derive the exact expressions of the mean,variance,and probability density function of the combining efficiency.The simulation results show that this model is valuable under the condition of the different number of aperture and signal-to-noise ratio combinations.Combining efficiency is also compared for Equal Gain Combining(EGC)diversity FSO systems with or without considering aperture selection.