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

ArticleinIEEE Antennas and Propagation Magazine 49(5):52 - 68 · November 2007with100 Reads
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.
    • "where a n is the nth excitation coefficient of the nth mode, which shows that a n of only a few modes, which have small eigenvalues, can contribute to total radiated field at a specific frequency [44]. V i n is the modal excitation coefficient which account for the way of position, magnitude, and phase of feed effect on each mode contribution to the total current [23]. The effect of antenna feed can be shown through input admittance at feed point (P) [22] "
    [Show abstract] [Hide abstract] ABSTRACT: In this paper, characteristic mode analysis (CMA) of three empirical design techniques for the probe-fed, symmetrically located, U-slot microstrip patch antenna, on a single-layer grounded substrate, is presented with supporting experimental data. The first method, resonant frequency (ResF), utilizes the existence of the four distinct ResFs, while the second one, dimensional invariance (DI), relies on the property of DI, for the design of the U-slot microstrip patch. In both these methods, the optimization of the probe location is necessary for further enhancement of the 10-dB return loss bandwidth. The third method, dimensionally invariant ResF, that optimally combines the features of the previous two is developed here and shown to yield better bandwidth performance with minimal or no probe location optimization, and hence is superior to the other two for rapid prototyping. CMA is carried out for critical parameters, such as substrate electrical thickness, slot width, probe radius, and feed location variations, to assess their dominant influence on the characteristics of the U-slot microstrip patch antenna.
    Full-text · Article · Jul 2016
    • "Physically, a characteristic angle models the phase difference between a characteristic current J n and its associated characteristic field E n [11]. At the resonance frequency, this phase difference is 180º. "
    [Show abstract] [Hide abstract] ABSTRACT: This paper describes the design and construction of a crossed slot antenna array to be applied to an Incoherent Scatter Radar for measuring parameters of the Ionosphere. The slot antenna was designed and optimized with electromagnetic simulation software. An analysis of the characteristic modes of the elementary antenna of the array is performed, in order to obtain a physical understanding of the radiating behavior. A prototype of a linear crossed-slot antenna array has been constructed and measured, as an intermediate step for the development of a two-dimensional array.
    Conference Paper · Apr 2016 · IEEE Transactions on Antennas and Propagation
    • "Although it is generally understood that low permittivity substrates contribute to bandwidth broadening due to low Q Factor, their resonant behavior is not well understood. One recently re-discovered tool that is helping antenna designers gain better understanding and physical insight of the radiating nature and resonant behavior of the microstrip patch antenna is the Theory of Characteristic Modes (TCM) [1][2][3][4][5][6]. Characteristic modes represent a set of orthogonal real currents on the surface of a conducting body. "
    Full-text · Conference Paper · Mar 2016 · IEEE Transactions on Antennas and Propagation
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