Research On OAM-MIMO Wirelss Transmission Technology Base On Sparse Array

The electromagnetic orbital angular momentum(OAM)has attracted much attention because of its independent and orthogonal characteristics of the eigenmodes,which can effectively improve the efficiency of the spectrum and the safety of information transmission.As a new degree of freedom,how to produce multi-modal OAM wave is a crucial issue.Conventional array-based OAM technology used circular arrays,which is inconvenient to combine with traditional multi-antenna multi-input multi-output(MIMO)systems based on rectangular arrays.In this thesis,aiming at designing an OAM-MIMO transmission technology based on rectangular MIMO antenna array,the basic theory of multi-modal OAM wave generated by rectangular antenna array is studied.The OAM wave optimization method based on sparse array is designed,and the multi-modal OAMMIMO multiplexing transmission technology based on rectangular array is studied.The main research work is summarized as follows:First,a novel method of generating OAM wave based on a large planar rectangular array is presented in this thesis.The amplitude and phase characteristics of OAM waves generated by a planar rectangular array with different array parameters are simulated and analyzed.It is proved that this method can effectively generate OAM waves with different modes.Secondly,in order to reduce the complexity of the system and solve the problem of side lobe level of OAM beams,sparse array technology to the optimization of OAM waves is applied in this thesis.At a certain sparse rate,the genetic algorithm is used to find the best sparse array,and the OAM wave can be generated on the sparse array while the beam optimization can be achieved.In addition,in order to be able to further optimize OAM waves,this thesis uses particle swarm optimization to optimize sparse array excitation.Simulated results show that comparing and analyzing the performance of OAM waves under different sparse rates and array excitation optimization,the elements number of 8?8 planar rectangular array are reduced by about 25%,and peak side lobe level is suppressed from-11.56 d B to-20.76 d B.In addition,compared with the ordinary planar array generating OAM waves,this method has the advantages of low cost and low complexity.Finally,based on the generation of multi-mode OAM waves based on rectangular arrays,establishing and analyzing the OAM-MIMO communication system model before and after sparse,and comparing the system channel capacity before and after sparse in this thesis.Simulated results show that as the signal-to-noise ratio and the number of transmitting antennas,the channel capacity of both will increase.In addition,for a wireless communication system in which an OAM wave with a mode of +1 or the multimodal OAM waves are multiplexed,while reducing the transmitting antennas,the sparse channel capacity is very close to original 8?8 array.This work will enhance the application of orbital angular momentum in existing massive MIMO or 2D arrays,and also help other technologies based on radio wave OAM,such as secure communication,quantum encryption,etc.