基于轨道角动量复用的声波通信特性及环形相控阵设计

Characteristics of acoustic communication based on orbital angular momentum multiplexing and design of circular phased array

为提高水下声波轨道角动量的通信性能,建立环形相控阵发射和圆面接收的通信模型,研究声波轨道角动量复用通信时的源头串扰特性;提出一种新的驱动方式以提高发射效率,并分析接收偏角对通信质量的影响。研究结果表明:当使用由N个不同发射源组成的环形相控阵产生l阶轨道角动量时,将同时产生c阶的轨道角动量串扰声束(其中c=l+bN,b为非零整数)。声源数N与声涡旋阶数l满足||l≤N/2,因此,在基于该环形相控阵的轨道角动量复用通信中,任意轨道角动量信道的串扰分量均在有用信道之外。使用N×M型环形相控阵(其中N为弧形声源组数,M为每组声源内的换能器数量)发射时,增大N和M均可提高发射效率,而当相控阵中换能器数量固定时,根据实际的需要合理选取N和M,有利于提高发射效率并降低阵列控制的复杂度,体现了控制设计的灵活性;随着接收偏角增大,通信性能整体下降。

In order to improve the performance of underwater acoustic orbital angular momentum(OAM)multiplexing communications,a communication model composed of a circular phased-array transmitter and a discshaped ideal receiver was established to study source crosstalk characteristics.A new driving method was proposed to improve transmit efficiency,and the influence of receiving deflection angle on communication quality was analyzed.The results show that when using a circular phased array composed of N different emission sources to generate l-order OAM,c-order OAM crosstalk beams will be generated simultaneously,where c=l+bN with b being a non-zero integer.There is a relational expression between the vortex's order l and the source number N,i.e.,|l|≤N/2,and so the OAM crosstalk components are out of the useful channels in OAM multiplexing communications based on the circular phased array.When using an N×M-type circular phased array which consists of N groups of arc-shaped sound sources with M transducers as a group for transmission,the increasing of N and M can improve transmission efficiency.When the total number of transducers in the emitter array is fixed,N and M should be properly chosen to balance transmission efficiency against the complexity of array control,which reflects the flexibility of the control design.The communication performance generally decreases with the increase of receiving deflection angle.