Stored Energies and Radiation Q

Abstract

This paper discusses the methods for evaluating the stored electromagnetic energies and the radiation Q for an arbitrary lossless antenna. New expressions for the stored electromagnetic energies are derived by using the Poynting theorem in the complex frequency domain, and they are compared with previous theory and are validated by numerical examples. The minimization of radiation Q is also investigated. There exists an optimal current distribution that minimizes the radiation Q for specified antenna geometry. The optimized Q and the optimal current distribution may be determined by solving a generalized eigenvalue equation obtained from the Rayleigh quotient for the radiation Q. Index Terms-Antenna theory, antenna Q, stored energy2          J r J r r r rr (6) T Region3 Antenna (scatterer) J imp J Feeding line Input terminal Impressed source Region1 Region2     J J J r J r J r J r J r J r J r J r

An Eigenmode Correlation‐Based Algorithm for Approaching Antenna Optimal Currents With Multiple Feeds

“…To avoid ambiguity, the letter s and the black arrow nearby in Figure 3a have indicated the reference starting point and the current display direction along the radiator in (b), respectively. The optimal current and Q of such a dipole have already been reported in Wen (2015), and one sees that with a single feed at the dipole center, a well-known triangular distribution is excited, and it can be taken as a reasonable approximation for J opt . Note that in Figure 3b, the single-feed module calculated [K 1 ] peak locates the single feed right at the center.…”

“…It essentially covers a wide range of practical antenna optimization problems, such as gain (G), quality factor (Q), G/Q, and radiation efficiency. These optimization problems, especially vital for electrically small antennas (ESAs), have been studied for decades, and great progress has been made (Chu, 1948;Cismasu & Gustafsson, 2014;Collin & Rothschild, 1964;Ethier & McNamara, 2014;Fante, 1969;Gustafsson et al, 2012;Gustafsson & Nordebo, 2013;Harrington, 1960;Jelinek & Capek, 2017;Kim, 2012Kim, , 2016McLean, 1996;Thal, 2006;Vandenbosch, 2011;Wen, 2013Wen, , 2015Yaghjian & Best, 2005).…”

“…The interior stored energy of a volumetric radiator has been eliminated with either an introduction of a loaded shell with extremely high permeability (Kim, 2012) or an optimization for both the electric and magnetic currents on the surface (Kim, 2016). Based on a closed-form solution of the radiated power and stored electric and magnetic energy of a radiator (Vandenbosch, 2010), an optimization for a maximal G and G/Q, a minimal Q, and a maximal radiation efficiency (η) has been completed (Cismasu & Gustafsson, 2014;Gustafsson et al, 2012;Gustafsson & Nordebo, 2013;Wen, 2013Wen, , 2015Jelinek & Capek, 2017). Among them, the optimization process is mainly based on a method of moments (MOM) formulation (matrix form of the operators) of the problem, and several optimization techniques such as variation method, Lagrange multipliers, and convex optimization are utilized.…”

Reply to “Comments on “Stored Energies and Radiation Q””

“…They have used some references (references 2 and 3 in [1]) to support their assertion and totally disregarded the discussions in the commented paper as well as in the related references [17] [18], which are missing in the reference section of the comment. We stress again that the Foster reactance theorem has been derived for an ideal antenna connected with a feeding waveguide in a single-mode operation.…”

“…We stress again that the Foster reactance theorem has been derived for an ideal antenna connected with a feeding waveguide in a single-mode operation. Although the feeding waveguide is assumed in the derivation of the Foster reactance theorem, we find, from numerous numerical simulations [6][17] [18], that the Foster reactance theorem also applies for an infinitely thin wire antenna excited by a delta function generator.…”