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The radiation from a conventional metamaterial loop antenna (metaloop) is circularly polarized within two frequency bands. This paper reveals that the radiation from a novel metaloop, where stubs are added to the loop arm, is circularly polarized within three frequency bands specified by the Nion frequency, Hion frequency, and upper band-edge frequency for a fast wave. The antenna characteristics,...
This paper presents the radiation characteristics of a low-profile circularly polarized loop antenna that has a left-handed property. The antenna height is set to be small (less than 0.03 wavelength). The gain, axial ratio, radiation efficiency, and VSWR are discussed.
The radiation from a metamaterial spiral (MTSP) is investigated. The MTSP radiates a left-handed circularly polarized (CP) wave, a right-handed CP wave, and a linearly polarized (LP) wave. Effects of antenna size on the antenna characteristics, including the radiation pattern, axial ratio, polarization, and gain, are discussed.
A low-profile cavity-backed spiral antenna with an absorbing strip exhibits wideband radiation characteristics. An EBG reflector is useful in designing a small spiral for medium frequency bandwidth operation. A modified EBG reflector contributes to mitigation of the partial deterioration of the antenna characteristics in a low-profile equiangular spiral antenna. The circularly polarized radiation...
A low-profile curl antenna with an EBG reflector has a relatively wide input impedance bandwidth. Low-profile equiangular- and Archimedean-spiral antennas, each backed by an EBG reflector, have a wider input impedance bandwidth than the curl. A low-profile inverted F antenna above an EBG reflector radiates a tilted beam. An array composed of inverted F antennas combined with switching circuits has...
Conventional spiral antennas radiate either a left-handed circularly polarized (CP) wave or a right-handed CP wave in a specific direction (single CP radiation). This letter presents a novel spiral antenna, designated as the metamaterial spiral, which radiates a dual CP wave. First, the principle for left-handed CP radiation and right-handed CP radiation is explained using “current bands.” Second,...
A structure composed of two fed arc strips and two parasitic arc strips, and an EBG reflector is investigated for realizing a horizontally polarized, omnidirectional antenna. The effects of the configuration parameters on the antenna characteristics are analyzed and discussed.
An extremely low-profile spiral antenna above a PEC reflector does not show wideband antenna characteristics. However, placing ring-shaped absorbing material between the outermost spiral arms and the PEC reflector mitigates deterioration in the antenna characteristics. Further investigation shows that removing absorbing material and replacing the PEC reflector by an EBG reflector contribute to realizing...
This paper presents a spiral antenna backed by a mushroom-shaped EBG reflector. The antenna characteristics are investigated on the basis of the electric and magnetic fields obtained by using the finite-difference time-domain method. The investigation reveals that removing some patches from the EBG reflector improves the axial ratio.
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