Study Of Theory Of Characteristic Mode And Its Application In Filtering Patch Antenna Design

In the past ten years,theory of characteristic mode(TCM)has shown unique value in guiding the design of antennas because it can intuitively provide clear physical characteristics of antennas,and has been widely used in the field of antenna.However,the accuracy of modal analysis is closely related to the modal tracking method.Therefore,designing an accurate,fast,simple and efficient modal tracking method is the key to the successful application of TCM.On the other hand,the wireless communication system is developing towards miniaturization and low loss,and the functional integrated devices that integrate two or more functions together have attracted more and more attention.Therefore,the filtering antenna has become a research hotspot in the current antenna field,among which,how to design the filtering antenna efficiently has always been a difficult problem.To this end,this paper studies the TCM and its application in filtering patch antenna design,proposes an advanced eigenvector correlation based tracking method for characteristic modes,and further proposes a TCM based design method for filtering patch antennas.The work of this paper is as follows:(1)An advanced eigenvector correlation based tracking method for characteristic modes is proposed.The tracking method can be divided into four parts: first calculate eigenvalues and eigenvectors,then preprocess the eigenvalues,then track the modes according to the largest correlation coefficient,and finally apply the tracking error correction algorithm(TECA).Among them,the proposed TECA is the core of the method.It is based on the mechanism of the occurrence of two tracking problems and ingeniously designed a table of eigenvalue difference between any two modes.By combining the change of sign and the change of difference of the mode pairs eigenvalue difference in the table can find the mode pairs that may happen mode swapping and mode degeneracy,and then judge whether there is an error in the tracking,and finally correct the error.Through the verification of two antenna examples,it is proved that the proposed method can effectively solve two common mode tracking problems:mode swapping and mode degeneracy.(2)An efficient TCM based design method for filtering patch antennas is firstly proposed.The method has three parts: firstly,use TCM to analyze the filtering antenna without feed structure to find the resonant modes in the passband and predict the position of the two inherent radiation nulls at high and low frequencies,and use them to assist in obtaining suitable radiator and filtering structure size;then use modal analysis to find the best feed position to excite the resonant modes and generate two inherent radiation nulls at the same time;finally,optimize the filtering antenna.Through the design of two filtering patch antennas,it is proved that the proposed method can realize the independent analysis and design of the antenna structure and feed,and make the design process of the filtering antenna clearer and more efficient.