Beam alignments based on the spectrum decomposition of orbital angular momentums for acoustic-vortex communications

Given the enhanced channel capacity of wave chirality, acoustic communications based on the orbital angular momentum (OAM) of acoustic-vortex (AV) beams are of significant interest for underwater data transmissions. However, the stringent beam alignment is required for the coaxial arrangement of transceiver arrays to ensure the accuracy and reliability of OAM decoding. To avoid the required multiple measurements of the traditional orthogonality based algorithm, the beam alignment algorithm based on the OAM spectrum decomposition is proposed for AV communications by using simplified ring-arrays. Numerical studies of the single-OAM and OAM-multiplexed AV beams show that the error of the OAM spectrum increases with the translation distance and the deflection angle of the transceiver arrays. To achieve an ideal arrangement, two methods of the single-array translation alignment and the dual-array deflection alignment are developed based on the least standard deviation of the OAM spectrum (SD-OAM). By decreasing the SD-OAM towards zero using transceiver arrays of 16 transmitters and 16 receivers, accurate beam alignments are accomplished by multiple adjustments in three dimensions. The proposed method is also demonstrated by experimental measurements of the OAM dispersion and the SD-OAM for misaligned beams. The results demonstrate the feasibility of the rapid beam alignment based on the OAM spectrum decomposition by using simplified transceiver ring-arrays, and suggest more application potentials for acoustic communications.     

环形稀疏声源阵列声涡旋的优化与操控

提出和优化了环形稀疏声源阵列涡旋声场的形成方法,进行了涡旋声压,相位和振动速度的理论推导和特性分析。通过改变声源数、声源频率和观测距离等参数,对声涡旋场的模拟结果证明,声涡旋半径主要由信号波长决定,声源频率越高,声涡旋半径越小,能量越集中;涡旋声压随着声源数的增加而线性提高,随着传播距离的增加而减小;声涡旋环形相位分布的线性度随着声源数、声源波长和传播距离的增加而提高。建立了3/4/6/8声源实验系统,径向声压和相位分布以及环形相位分布的测量结果和模拟结果具有较好的一致性,同时悬吊泡沫盘的旋转证明了声涡旋角动量的传输。本研究中声涡旋场的特性分析和参数优化为粒子操控及其在生物医学中的应用提供了依据。