Research On Vortex Acoustic Field Manipulation And Coding Communications

With the increasing frequency and rapid development of global marine activities,the modern marine communication networks and technologies have become the subjects of great concern in the academia and industry.Particularly,underwater wireless communication is the key technology for marine communication.Generally,it can be mainly divided into underwater optical communication,underwater electromagnetic wave communication and underwater acoustic communication.Among them,light wave and electromagnetic wave are difficult to propagate over a long distance in the underwater environment due to strong scattering,while acoustic wave has smaller loss in the process of underwater propagation.Hence,underwater acoustic communication could be an ideal way for underwater long-distance communication.Due to the complex and changeable marine environment,the amplitude and phase distribution of Gaussian sound field would become disorderly after underwater transmission,which will adversely affect the quality of soundbased communication.In addition,the carrier frequency in underwater acoustic communications is usually very low,which also greatly limits the data transmission capacity.In view of this,there are some important issues that need to be solved urgently in the application of underwater acoustic communication,such as how to flexibly regulate the sound field and how to greatly increase the data transmission capacity in the underwater acoustic communications with low carrier frequency.In this dissertation,the research of vortex sound field control and coding communication is carried out.The specific contents are as follows:1)The advantages of acoustic waves in underwater communication and detection(compared with light waves and electromagnetic waves)are analyzed.Additionally,the background of vortex acoustic field is introduced,and the influence of the underwater environment on the transmission loss for different frequency waves is discussed.Furthermore,the transmission capacity of underwater acoustic communications is introduced.2)The acoustic pressure wave equation is deduced.In addition,the acoustic pressure equations of plane waves and spherical waves radiated by point acoustic sources are obtained using the transmission characteristics of plane waves and spherical waves.Furthermore,the transmission characteristics of the Gaussian acoustic field are analyzed,and the theory and characteristics of the vortex acoustic field are also studied.3)The research on control of the free space vortex acoustic field.The methods for control and production of the vortex acoustic field are introduced,and the amplitude and phase characteristics of the vortex acoustic field generated by the speaker array are simulated based on the theory of the vortex acoustic filed.In addition,the corresponding installation frame is designed according to the size of the speaker array,and we experimentally measured the effects on the amplitude and phase characteristics of vortex acoustic field with the frequency of acoustic field,transmission distance and topological charge.Finally,according to the theory and characteristics of scattered acoustic filed,the method and system for adaptive acoustic field control are proposed,and the reconfigurable acoustic element is further used to replace the array acoustic source to realize the self-adaptive regulation from the use of neural network to establish the corresponding relationship between the input acoustic field and the output acoustic field.4)The research on the free space coding communication with vortex acoustic field.Based on the orthogonality between different orders of orbital angular momentum,we proposed the method for information transmission based on phased array coding,and simulated the coding communication and image transmission using vortex acoustic field.In addition,we designed and manufactured the transmitter circuit for encoding communication with vortex acoustic field,including power supply circuit,clock circuit,configuration and download interface circuit,extended version interface,output circuit for sinusoidal signal,the receiving,acquisition and post-processing modules for coding communication with vortex sound field,and the transmission and reception of the letter information is verified in experiments.Finally,the communication concept and system using structured acoustic field is proposed for real-time communication.