Design Of Patch Antenna Based On The Theory Of Characteristic Mode

The Theory of Characteristic Mode(TCM)is a method of insight into the radiation properties of the object itself.It can reflect the true radiation potential of the conductor without excitation.Using TCM to guide antenna design can not only significantly improve design efficiency and reduce the blindness of violent scanning,but also provide designers with clearer and more intuitive arguments for understanding the principle of conductor radiation.Therefore,the application of TCM has become one of the current trends in the research and design of many complex antennas.Based on the numerical derivation method of TCM,this paper tries to solve the problem of mode crosstalk when drawing eigenvalue curve.By applying and improving the one-dimensional information entropy algorithm,adding the relevant logic of "predecision",a new mode tracking algorithm is developed,which can significantly reduce the time spent on existing mode tracking algorithm.Then the TCM is applied to the design of circularly polarized antenna.Based on the analysis of the characteristic modes of the ring patch,the ring traveling wave mode to be directly excited is found out.So,we design a capacitor coupling feed to match it.Thus,a single-fed ring broadband circularly polarized antenna with a relative impedance bandwidth of 24%and a relative axial ratio bandwidth of 13.5%operating at 2.4GHz frequency band is realized.Finally,the TCM is used to guide the design of the orbital angular momentum antenna.First,a simple square patch is used as the starting point for the research.Through the analysis of the characteristic mode of the conductor,the goal is to excite the two fundamental modes and realize the mode synthesis.We design a bending microstrip feeding to degenerate two fundamental modes which have 90° phase shift between each other.So,we realize an orbital angular momentum antenna that can radiate zero-order vortex waves.Afterwards,irregular hexagonal conductor sheets were used.According to the analysis of its characteristic modes,the starting point is to simultaneously excite two fundamental modes and two higher-order modes.Using the same bent microstrip singlefed to degenerate characteristic modes,we design a dual-frequency orbital angular momentum antenna that radiates zero-order and first-order eddy waves in turn at different frequency points.At the same time,the model verification is carried out with the TCM method,and the design thinking summary of the TCM method is finally completed.