Topic
Circular polarization
About: Circular polarization is a research topic. Over the lifetime, 15201 publications have been published within this topic receiving 234418 citations.
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TL;DR: In this article, the axial or beam mode of a long helix is analyzed, and the importance of the array factor in determining the radiation pattern is discussed, as well as the conditions for circular polarization.
Abstract: The helix is a fundamental form of antenna of which loops and straight wires are limiting cases. When the helix is small compared to the wavelength, radiation is maximum normal to the helix axis. Depending on the helix geometry, the radiation may, in theory, be elliptically, plane, or circularly polarized. When the helix circumference is about 1 wavelength, radiation may be maximum in the direction of the helix axis and circularly polarized or nearly so. This mode of radiation, called the axial or beam mode, is generated in practice with great ease, and may be dominant over a wide frequency range with desirable pattern, impedance, and polarization characteristics. The radiation pattern is maintained in the axial mode over wide frequency ranges because of a natural adjustment of the phase velocity of wave propagation on the helix. The terminal impedance is relatively constant over the same frequency range because of the large initial attenuation of waves on the helix. The conditions for circular polarization are analyzed, and the importance of the array factor in determining the radiation pattern of a long helix is discussed.
157 citations
TL;DR: In this article, a bi-layered linear-to-circular (LTC) polarization conversion metasurface operating in 11.4-14.3 GHz is designed and fabricated, which is composed of two layers of metallic pattern arrays separated by a 1.5mm-thick dielectric spacer.
Abstract: In this paper, we propose to achieve wideband linear-to-circular (LTC) polarization conversion by ultra-thin bi-layered metasurfaces. As an example, an LTC polarization conversion metasurface operating in 11.4–14.3 GHz is designed and fabricated, which is composed of two layers of metallic pattern arrays separated by a 1.5 mm-thick dielectric spacer. When linearly polarized waves impinge on the bi-layered metasurface, LTC polarization conversion transmission is greater than 90% over a wide frequency range from 11.0 GHz to 18.3 GHz. Meanwhile, the axis ratio is lower than 3 dB in 9.8–18.3 GHz. This wide-band and highly efficient LTC polarization conversion transmission is analyzed theoretically. The measured LTC polarization conversion transmissions are well consistent with the simulated results.
156 citations
TL;DR: In this article, a dual-band dual-sense circularly-polarized CPW-fed slot antenna with two spiral slots loaded is presented, where the two loaded spiral slots in the ground plane can result in different senses of circular polarization.
Abstract: A novel design of a dual-band dual-sense circularly-polarized CPW-fed slot antenna with two spiral slots loaded is presented. The two loaded spiral slots in the ground plane can result in different senses of circular polarization. The dual-band operation is achieved by using the T-shape strip. The ratio of two frequencies is 1.375. The antenna is designed, fabricated, and measured. It is shown that the proposed antenna has good circular polarization characteristic. The measured 10 dB return loss impedance bandwidths are 8.7% for the lower band (RHCP) and 23% for the upper band (LHCP). The measured 3 dB axial-ratio bandwidths are 8.4% and 19.24%, with respect to 1.6 GHz (RHCP) and 2.2 GHz (LHCP), respectively.
155 citations
TL;DR: The strongly modulated circular patterns for monolayer (bilayer) graphene rotate by ±90° (±45°) in changing from linearly to circularly polarized light; these angles are directly related to the phases of the wave functions and thus visually confirm the Berry's phase of π (2π) around the Dirac point.
Abstract: Electronic chirality near the Dirac point is a key property of graphene systems, which is revealed by the spectral intensity patterns as measured by angle-resolved photoemission spectroscopy under various polarization conditions. Specifically, the strongly modulated circular patterns for monolayer (bilayer) graphene rotate by ±90° (±45°) in changing from linearly to circularly polarized light; these angles are directly related to the phases of the wave functions and thus visually confirm the Berry's phase of π (2π) around the Dirac point. The details are verified by calculations.
155 citations
TL;DR: In this paper, a two-dimensional anisotropic periodic structure composed of arrays of subwavelength capacitive patches and inductive wire grids separated by thin dielectric substrates was designed to behave differently for field components of the two orthogonal polarizations and transmitted a circularly polarized wave once illuminated by a linearly polarized plane wave.
Abstract: We introduce a new technique for designing wideband polarization converters based on miniaturized-element frequency selective surfaces (MEFSSs). The proposed structure is a two-dimensionally anisotropic periodic structure composed of arrays of subwavelength capacitive patches and inductive wire grids separated by thin dielectric substrates. The structure is designed to behave differently for field components of the two orthogonal polarizations and transmits a circularly polarized wave once illuminated by a linearly polarized plane wave. Using equivalent circuit models for MEFSSs, a synthesis procedure is developed that can be used to design the polarization converter from its required bandwidth and center frequency of operation. Using this procedure, a prototype of the proposed polarization converter operating within the X-band is designed, fabricated, and experimentally characterized using a free-space measurement system. The measurement results confirm the theoretical predictions and the design procedure of the structure and demonstrate that the proposed MEFSS-based polarization converter operates in a wide field of view of $\pm45^{\circ}$ with a fractional bandwidth of 40%.
155 citations