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The frequency-dependent finite-difference time-domain (FDTD) method has widely been used to treat dispersive materials, e.g., metal at optical frequencies, semiconductors at THz frequencies, water at microwave frequencies, and so on. Unfortunately, the time step size is restricted by the Courant-Friedrichs-Lewy (CFL) condition even for the frequency-dependent FDTD method. To remove this restriction,...
This paper discusses an antenna system composed of a fed metaspiral element and two dielectric slabs above the spiral. Analysis reveals that the slabs lead to an increase in the gain, in accordance with the formation of a narrow radiation beam. A gain of 6.5 dBi is obtained, which is 6.5 dB higher than the gain in the absence of the slabs.
A novel helical antenna, designated as the metahelical antenna, is proposed, where the helical arm has electromagnetic right-handed (RH) and left-handed (LH) properties. The antenna design process is described. It is found that the metahelical antenna radiates a circularly polarized (CP) wave within two frequency bands. The rotational sense of the CP wave within one of the frequency bands is opposite...
Power conserving property of the propagating transverse-magnetic wave in a strongly guiding waveguide is demonstrated using the beam-propagation method with a transformed field. A step-index profile is expressed by a sigmoid function. A tilted, asymmetrical waveguide and a Y-branching waveguide with high index contrast are analyzed and discussed.
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