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A hepta-band antenna with high efficiency, small clearance, and simple structure for metal-rimmed smartphones is proposed in this letter. The proposed antenna occupies only 71 × 5 mm2 of the total clearance, and it is mainly composed of a system ground, a metal rim with two gaps, and two shorting strips. The theory of characteristic modes is used to analyze the entire structure. All resonant characteristic modes (CMs) in the target frequency are traced, and their characteristic current distributions are analyzed. By using an L-shaped capacitive exciter, three CMs are excited at the lower bands, and an inverted L-shaped branch is utilized for improving the impedance matching at higher bands. The measured 6 dB impedance bandwidths were 800–1000 and 1700–2780 MHz, respectively, and they can cover seven operating bands. The measured efficiencies were 62%–85.7% at the lower band and 66.9%–91% at the higher band. [ABSTRACT FROM AUTHOR]

In this letter, new metrics are proposed to provide physical insight into the behavior of metamaterial-based structures by means of the theory of characteristic modes. A relationship between the first eigenmode and an expression of the polarizability is proposed for a split-ring resonator. It thus allows us to describe a link between the artificial magnetic response of a split-ring resonator and modal characteristics. Using the new metrics proposed, a reactive impedance substrate based on metal-dielectric metamaterial excited by a parallel magnetic field is shown to exhibit artificial magnetism. These metrics are shown to propose good agreement with other analytical and numerical methods. This analysis should be useful when such metal-dielectric metamaterial structures are associated to radiating elements like antennas since it could be performed in the near-field region, unlike common approaches based on plane wave and far-field assumptions. [ABSTRACT FROM PUBLISHER]

In this letter, we propose a horizontally polarized antenna with omni-directivity in horizontal plane. Ripple coefficient of the radiation pattern in horizontal plane improves up to ±0.1 dB. The theory of characteristic modes is used to analyze and illustrate the reason for why the omni-directivity property of the proposed antenna improved. Finally, we verify the antenna performances by experiment. [ABSTRACT FROM AUTHOR]