Characteristic mode analysis

Abstract: At a given frequency every perfectly conducting obstacle has associated with it a particular set of surface currents and corresponding radiated fields which are characteristic of the obstacle shape and independent of any specific excitation. These characteristic modes form a useful basis set in which to expand fields radiated or scattered at a great distance from the obstacle. Once these modes are known for a given obstacle, the scattering of plane waves incident from arbitrary source directions into arbitrary receiver directions may be evaluated concisely. To support the theory, a method is described for determining characteristic mode currents on thin wires of general shape and is applied to several shapes to generate certain backscattering and input admittance data. Wherever possible comparison is made with existing data.

Abstract: 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.

Abstract: A procedure for computing the characteristic modes for conducting bodies of arbitrary shape is developed. The method is applied to conducting bodies of revolution and to wire objects, and general computer programs are discussed. Illustrative examples of the computation of characteristic currents and characteristic fields are given for a cone-sphere, a disk, and a wire arrow. Modal solutions using these modes are computed for representative antenna and scattering problems to illustrate convergence of the solution as the number of modes is increased.

Abstract: This book examines both theoretical developments of characteristic modes (CMs) and practical developments of CM-based methodologies for a variety of critical antenna designs. The book is divided into six chapters. Chapter 1 provides an introduction and discusses the recent advances of the CM theory and its applications in antenna engineering. Chapter 2 describes the formulation of the characteristic mode theory for perfectly electrically conducting (PEC) bodies and discusses its numerical implementations. Chapter 3 presents the CM theory for PEC structures embedded in multilayered medium and its applications. Chapter 4 covers recent advances in CM theory for dielectric bodies and also their applications. Chapter 5 discusses the CM theory for N-port networks and its applications to the design of antenna arrays. Finally, Chapter 6 discusses the design of platform-integrated antenna systems using characteristic modes.