The Theory of Characteristic Modes Revisited: A Contribution to the Design of Antennas for Modern Applications

Univ. Politecnica de Valencia, Valencia
IEEE Antennas and Propagation Magazine (Impact Factor: 1.32). 11/2007; 49(5):52 - 68. DOI: 10.1109/MAP.2007.4395295
Source: IEEE Xplore


The objective of this paper is to summarize the work that has been developed by the authors for the last several years, in order to demonstrate that the Theory of Characteristic Modes can be used to perform a systematic design of different types of antennas. Characteristic modes are real current modes that can be computed numerically for conducting bodies of arbitrary shape. Since characteristic modes form a set of orthogonal functions, they can be used to expand the total current on the surface of the body. However, this paper shows that what makes characteristic modes really attractive for antenna design is the physical insight they bring into the radiating phenomena taking place in the antenna. The resonance frequency of modes, as well as their radiating behavior, can be determined from the information provided by the eigenvalues associated with the characteristic modes. Moreover, by studying the current distribution of modes, an optimum feeding arrangement can be found in order to obtain the desired radiating behavior.

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    • "T HE theory of characteristic modes (CMs), formally developed by Garbacz [1] and Harrington and Mautz [2], has become very popular in recent years as this theory constitutes a general approach to characterizing the modal resonant behavior of arbitrarily shaped antennas and scaterrers [3]. In its original form, which is considered here, the CM assumes perfectly conducting electric conductors (PEC) in a vacuum. "
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    ABSTRACT: Aspects of the theory of characteristic modes, based on its variational formulation, are presented and an explicit form of a related functional, involving only currents in a spatial domain, is derived. The new formulation leads to deeper insight into the modal behavior of radiating structures as demonstrated by a detailed analysis of three canonical structures: a dipole, an array of two dipoles and a loop. Important numerical aspects related to modal superposition and the residual ("evanescent") mode are also considered. It is shown that due to numerical issues, certain modes may actually exhibit incorrect (negative) radiated power, which, in turn, destabilize the solution of the generalized eigenvalue problem. A simple solution, based on splitting the superposition into two parts, is proposed.
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    • "Later, Harrington, Mautz and Chang reformulated this theory considering integro-differential formulations using the impedance matrix of the Method of Moments (MoM), [2], [3]. Recently, there have been many works on metal structures [4], and it is now being extended to applications including dielectric materials. For both metals and dielectrics it is important to find those electromagnetic modes that provides the desired radiation characteristics, and this is where the CMT plays an important role. "
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    ABSTRACT: In this paper Complex Natural Resonances of an infinite dielectric circular cylinder based on the PMCHWT formulation are presented. The relation between them and the Characteristic Mode resonances are explained. In addition, the reasons for different characteristic modes using different integral equations are explained. A connection between the resonances of series solution and integral formulations are carried out.
    IEEE International Symposium on Antennas and Propagation and USNC-URSI National Radio ScienceMeeting, Vancouver (Canada), July, 2015.; 07/2015
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    • "The theory of characteristic modes was studied more than four decades ago but was only recently applied in the design and analysis of antennas [4]. The theory helps in the systematic design and analysis of antennas by computing the orthogonal current modes, that are supported by the antenna structure. "
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    ABSTRACT: A miniaturized microstrip patch antenna (MPA) design is analyzed using the theory of characteristic modes. The miniaturization is achieved by using an annular slot in the ground plane of the MPA. The theory of characteristic modes is applied to understand the resonant behavior of the antenna and to find the optimal location for the excitation of the antenna. Using this method, a 46% miniaturization in the size of MPA is achieved.
    2015 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting; 07/2015
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