A systematic design of dual-band, orthogonally-polarized linear-to-circular polarization (LP-to-CP) converters is proposed. This class of polarization converters can transform linearly polarized ...waves into right- and left-hand circularly polarized (RHCP and LHCP) waves in two separate non-adjacent frequency bands. The reported polarizer is made of three cascaded bianisotropic sheet admittances, spaced by two isotropic dielectric slabs. The electromagnetic problem is studied using impedance boundary conditions. A transmission-matrix analysis of periodically-loaded transmission lines is employed in the design. An analytic model is developed, and closed-form expressions are derived for the frequency response of each sheet admittance. This method avoids the use of multi-parameter optimization procedures. An example of a dual-band, orthogonally-polarized LP-to-CP converter is proposed for satellite communication applications in the K-/Ka -band. The polarizer separately performs LP-to-LHCP and LP-to-RHCP conversions over the transmit (TX) and receive (RX) channels of the K-/Ka -band. The design is validated with a prototype. Under normal incidence, the polarizer exhibits axial ratio (AR) lower than 3 dB over the 18-22.2 (~21%) and 28.7-30.4 GHz (~6%) bands. The total transmission is above −1 dB within the same two bands. The performance is stable for scanning angles up to ±45°. For a 45° angle of incidence, the AR is lower than 3 dB in the bands 17-22 (~25.6%) and 28.6-30 GHz (~4.7%) with a total transmission higher than −1.2 dB.
Many wireless communication applications such as satellite communications use circularly polarized (CP) signals, with the requirement for easy switching of the polarization sense between uplink and ...downlink. Specifically, in satellite communications, the trend is also to move to higher frequencies and integrate the receiving and transmitting antennas in one dual-band terminal. However, these simultaneous demands make the design and fabrication of the composing parts very challenging. We propose, here, a dual-band dual-linear polarization (LP)-to-CP converter that works in the transmission mode. The working principle of this polarizer is explained through an example for Ka-band satellite communications at 19.7–20.2 and 29.5–30 GHz. The LP-to-CP converter is a single panel composed of identical unit cells with a thickness of only 1.05 mm and a size of 5.3 mm Formula Omitted mm. Due to its operation in the transmission mode, the polarizer can be combined with a simple dual-band dual-LP antenna to obtain the desired dual-band dual-CP single antenna. However, the unique property of this polarizer is yet the fact that it converts a given LP wave, e.g., x-polarization, to orthogonal CP waves at the two nonadjacent frequency bands, e.g., left-handed CP at lower band and right-handed CP at higher band. The polarizer is tested both with 20 and 30 GHz LP rectangular horns to illuminate a dual-band transmit array (TA) to obtain wide-angle steering of CP beams. The performance of the polarizer and its association with the TA is evaluated through simulation and measurements. We also present design guidelines for this type of polarizer.
Organic Electronics. In their Communication (e202202977), Zikai He et al. report on the circularly polarized room‐temperature phosphorescence of a bidibenzob,dfuran scaffold with locked axial ...chirality.
A square-shaped patch antenna with high-gain performance and polarization reconfigurability is introduced in this study. This antenna offers the unique capability of seamlessly transitioning between ...linear polarization (LP) and circular polarization (CP), expanding its versatility in various communication applications. The polarization flexibility is achieved through the strategic integration of two RF switches utilizing p-i-n diodes, strategically positioned within the square slot structure. Through meticulous optimization of the switch placement, the antenna is capable of generating both right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP) patterns. Fabrication and testing of the prototype validate the efficacy of the design, showcasing excellent agreement between simulated and measured results. Notably, the antenna demonstrates impressive impedance bandwidths of 5.6 %, 5.2 %, and 6.5 % at a nearly common frequency of 2.7 GHz, coupled with respectable gains of 8.12dBi for LP, 11.19dBic for LHCP, and 10.55dBic for RHCP configurations, respectively. The comprehensive design details, along with extensive experimental and simulated findings, are meticulously presented, underscoring the antenna’s remarkable performance and potential for diverse wireless communication scenarios.
A novel metallo-dielectric Huygens' unit cell is proposed that can be designed to operate either as a quarter-wave plate (QWP) or as a half-wave plate (HWP). The unit cell is based on a single-layer ...perforated dielectric, with straight (non-metallized) and 45° (metallized) elliptical holes. The novelty of the unit cell is its suitability for millimeter-wave implementation in printed-circuit board (PCB) fabrication due to the absence of metallic patterns of small line widths and gaps. As an example of their applicability, the wave plates are demonstrated in the near-field of 60-GHz band diffusion-bonded slot array antennas. The unit cell operating as a QWP is demonstrated in full-wave simulations and experimentally for linear-to-circular polarization conversion, whereby the combination of a linearly-polarized (LP) antenna and the QWP produces a circularly-polarized (CP) wave. Measurement results of the antenna and the QWP show ≤ -10-dB reflection from 59 to 63 GHz (6.6%), ≤ 3-dB axial ratio from 59.5 to 61.5 GHz (3.3%), and an overall efficiency ≥ 77% from 59.5 to 61.5 GHz. The unit cell operating as a HWP is demonstrated in full-wave simulations for polarization rotation of the LP antenna, and for changing the sense of rotation of a right-hand CP antenna into left-hand circular polarization.
Drastic enhancements in both emission intensity and circular polarization of a Eu( iii ) complex were achieved in 1-butanol solution in the presence of alkylammonium ions.
A multifunctional reconfigurable metasurface based on liquid metal injection is presented. The reflective flexible material metasurface formed by two switchable microfluidic layers- the top layer ...comprising an array of meandered half-rings and the lower layer, straight meander lines-can be reconfigured into four states. The proposed metasurface becomes a reflector with emptied channels, whereas it exhibits linear-to-circular polarization conversion (or linear-to-cross-polarization conversion) properties when the top (or bottom) layer is filled with a liquid metal alloy. Upon normal excitation of linearly u/v-polarized waves and activation of the bottom layer, the metasurface reflects cross v/u-polarized waves in the frequencies from 9.83 to 17.42 GHz (53% bandwidth) with a polarization conversion ratio (PCR) of at least 90%. On the other hand, the metasurface operates as a linear-to-circular polarizer (for u/v-polarized waves) over 8.97-11.30 GHz (23% bandwidth), reflecting left- or right-hand circularly polarized waves. To verify the polarization conversion performance, a <inline-formula> <tex-math notation="LaTeX">25\times 25 </tex-math></inline-formula> element metasurface array is fabricated and measured. The experimental results confirm the simulation results over the 8-12 GHz test band. The compactness, structural flexibility, and multifunctionality of the proposed metasurface make it a suitable candidate for modern integrated antenna array systems.
Invited for the cover of this issue is the group of Koji Miki, Kouichi Ohe, and colleagues at Kyoto University. The image depicts mythical dragons as carbon‐based double helicates. Read the full text ...of the article at 10.1002/chem.201901467.
“a “flexible” carbon‐based double helicate, that dynamically forms an intramolecular excimer under photoirradiation, has been developed. Furthermore, the intramolecular excimer emits strong near‐infrared circularly polarized luminescence. This report offers the new approach to prepare near‐infrared CPL emitters.” Read more about the story behind the cover in the Cover Profile and about the research itself on page 9211 ff. (DOI: 10.1002/chem.201901467).
Enantiopure irida6helicenes combining chirality at the metal center and at the helicenic fragment are obtained by dynamic kinetic resolution of configurationally labile 4helicenic ligands. These ...compounds exhibit perfect mirrored electronic circular dichroism (ECD) and circularly polarized phosphorescence (CPP) signals, as described by Carlos M. Cruz, Fernando P. Cossío, Zoraida Freixa, and co‐workers in their Communication (e202406663).
Today, it is well known that light possesses a linear momentum that is along the propagation direction. Besides, scientists also discovered that light can possess an angular momentum, a spin angular ...momentum (SAM) associated with circular polarization and an orbital angular momentum (OAM) owing to the azimuthally dependent phase. Even though such angular momenta are longitudinal in general, an SAM transverse to the propagation direction has opened up a variety of key applications1. In contrast, investigations of the transverse OAM are rare due to its complex nature. Here, we demonstrate a three-dimensional wave packet that is a spatiotemporal (ST) optical vortex with a controllable purely transverse OAM. Contrary to the transverse SAM, the magnitude of the transverse OAM carried by the ST vortex is scalable to a larger value by simple adjustments. Since the ST vortex carries a controllable OAM uniquely in the transverse dimension, it has strong potential for novel applications that may not be possible otherwise. The scheme reported here can be readily adapted for other spectral regimes and different wave fields, opening opportunities for the study and applications of ST vortices in a wide range of areas.By applying a spiral phase in a pulse shaper, a three-dimensional wave packet, which is a spatiotemporal optical vortex with a controllable purely transverse orbital angular momentum, is demonstrated.
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