Theory Of Characteristic Mode And Its Application In Antenna Design

Theory of Characteristic Mode(TCM)provides new guidelines for antenna design.The characteristic mode is the inherent attribute of the conductor structure itself,and the distribution of each characteristic mode on the conductor can be seen without the excitation.Applying the TCM to the antenna design can greatly improve the antenna design efficiency and provide a clear principle analysis.TCM can be widely applied to single conductor or multiconductor,whether planar structures or three-dimensional structures.This paper focuses on the application of the TCM.According to the characteristics of the conductor structure with different space complexity,combined with the characteristics of the different conductor structures,three antennas with different functions are designed.The paper first designs a single-mode antenna using a single metal plate.The mode 1 of the metal plate is excited by the coupling structure,and the proportion of the mode 1 is increased by using the two excitations in the same phase.A single-mode antenna was quantitatively analyzed and the mode-weighted coefficient was used to determine that mode 1 accounted for 93%of the total antenna radiated power.In addition,the single mode antenna based on the eigenmode theory is compared with the traditional IFA antenna to obtain the difference between the two antennas in principle.Then using the characteristic modes on the folded metal plate,a patch antenna structure with a ground radiation patch and a patch radiation pattern is designed to realize a dual-mode patch antenna with wideband characteristics.For the problem of weak radiative resonance of ground radiation mode,the electric field distribution characteristics and resonance characteristics of the antenna are analyzed in detail.The field distribution model of the antenna in the radiation mode is given.The initial structure is improved and the physical verification is processed.A miniaturized patch antenna structure with a working bandwidth of 21.1%was obtained.At last,the characteristic modes analysis of the three-dimensional three-sided structure is performed.By the characteristics that the far-field electric field of the characteristic modes are orthogonal to each other,a three-dimensional structure circular polarized antenna is designed.In the antenna design process,the differences in the weighting coefficients of the different feeding method are compared.Finally,the coaxial feed is used to excite the two resonant modes in a similar manner.The performance of the antenna is in accordance with the requirements of the circularly polarized antenna,and the analysis of the three-dimensional surface on antenna performance.