Characteristic Mode Tracking And Design Of OAM Mode Circular Patch Antenna

Traditional antenna design generally requires antenna designers repeatedly improve and optimize the antenna structure to achieve the required performance.In this process,there is no corresponding analysis of the characteristics of the radiator that constitutes the antenna.Characteristic mode theory allows us to define the physical characteristics of the radiator without excitation,which has a great guiding role in antenna design.Characteristic mode theory is applicable to any shape of planar or threedimensional conductor structure.Characteristic mode analysis can greatly reduce the workload of antenna design and debugging.Especially under the current challenges of higher and higher antenna performance and more and more complicated structure,characteristic mode analysis is increasingly applied to the design of various antennas.With the rise and development of various modern communication technologies,spectrum resources are facing exhaustion,and existing multiplexing technologies based on frequency,time,and space are far from meeting people's demand for communication rates.In theory,the electromagnetic wave that carries orbital angular momentum(OAM)has an infinite number of orthogonal modes at the same frequency,which provides us with a new multiplexing technology to improve the spectrum utilization rate of the communication system.The effective generation of orbital angular momentum is the basis of this communication method.Therefore,the design of orbital angular momentum antenna has become a current research hotspot.Mode tracking is a key issue in the application of characteristic mode theory.In this thesis,based on the cosine similarity between the modes,the corresponding mode tracking algorithm is written and verified in typical two-dimensional or threedimensional structures,and it is pointed out that the 3/2 proportional relationship between the maximum size of the structure and the minimum operating wavelength can be used to improve the processing efficiency of the algorithm.Based on the OAM mode synthesis theory,combined with the characteristic mode theory,this thesis carried out the construction of a single patch antenna OAM radiation.Introducing a circular arc segment outside the circular patch,it is easy to generate various low-order OAMcarrying waves by adjusting the arc segment.Experimental results show that the fundamental mode synthesis of circular radiation patch can only generate zero-order OAM mode,and the addition of an additional 90-degree phase shift to the degenerate modes of TM21 or TM31 can easily radiate first-order or second-order OAM-carrying waves.Based on the symmetrical loading of the circular arc segment,a second-order OAM antenna with controllable rotation direction is also constructed;based on the adjustment of the effective length of the circular arc segment,an OAM antenna with controllable order is constructed.Based on the regular hexagonal radiation patch,the analysis of high-order(fourth and sixth order)OAM antennas has also been carried out,and some results have been achieved,but the performance needs to be further improved.This thesis applies cosine similarity to characteristic mode tracking for the first time,which reduces the complexity of algorithm implementation to a certain extent.This thesis uses a single antenna to achieve OAM-carrying wave with different modes,which will greatly simplify the implementation architecture of the OAM system.