摘要 :
This literature presents a comprehensive, technical review of circularly polarized (CP) antennas for different applications in wireless communication, emphasizing on the recent developments in the concerned research. The article a...
展开
This literature presents a comprehensive, technical review of circularly polarized (CP) antennas for different applications in wireless communication, emphasizing on the recent developments in the concerned research. The article also presents a comparative study of various works reported in the open literature, with an aim to highlight the contribution of CP antenna systems in the chronological development of the wireless communication technology. The primary motive of this review is to (a) highlight the methodologies used by different researchers to portray and analyze the different aspects in which CP antennas find their applications in modern-day wireless communication, (b) provide a practical viewpoint of the future scope of the study, based upon the past and present state-of-art research trends and (c) provide a conceptual and technical support to present-day antenna designers to help the process of furtherance of innovation and multiple system integration. In conclusion, the article also throws some light upon the future scope of research in the vast domain of CP antenna applications.
收起
摘要 :
A comparison is presented of the effects of particle size, concentration, and detector depth on side scattering for linearly and circularly polarized incident Light. The scattering medium consists of various concentrations of part...
展开
A comparison is presented of the effects of particle size, concentration, and detector depth on side scattering for linearly and circularly polarized incident Light. The scattering medium consists of various concentrations of particles, which are either 1.24, 0.494, 0.36, 0.123, or 0.065 mu m in diameter, and which were mixed into filtered, distilled water and serve as the scattering centers. The results indicate that when this scattering medium is irradiated with linearly polarized laser light whose beam has been put through a quarter-wave plate in an effort to produce circularly polarized light, then there are two components scattered 90 degrees, that is, circularly and linearly polarized light. The amount of each component and the ratio to total intensity of scattered light are analyzed for the different particles. [References: 16]
收起
摘要 :
Asymmetric 2,7-di-tert-butyl-10b,10c-dimethyl-2',3'-dimethyl-pyrazino[2,3-e]dihydropyrene (DMPZ-DHP) was prepared by the annulation of diamino dihydropyrene with 2,3-butanedione. Optical resolution was achieved using chiral high-p...
展开
Asymmetric 2,7-di-tert-butyl-10b,10c-dimethyl-2',3'-dimethyl-pyrazino[2,3-e]dihydropyrene (DMPZ-DHP) was prepared by the annulation of diamino dihydropyrene with 2,3-butanedione. Optical resolution was achieved using chiral high-performance liquid chromatography systems after the photoisomerization of DMPZ-DHP to DMPZ-metacyclophane-diene (MCPD), and its Kuhn's anisotropy factor (g = Delta epsilon/epsilon) was determined to be approximately 1.0 e(-3) at 550 nm. [S]- and [R]-DMPZ-DHP were irradiated with 550nm left and right circularly polarized light (CPL), and photoisomerization was found to proceed more rapidly upon irradiating the [S]-isomer with right-CPL than with left-CPL and upon irradiating the [R]-isomer with left-CPL than with right-CPL. This suggests that CPL can be detected and analyzed using asymmetric DMPZ-DHP. (C) 2022 Published by Elsevier Ltd.
收起
摘要 :
We present previously unpublished circular polarization (cp) measurements at 4.8 and 8.0 GHz made with the University of Michigan 26-meter prime focus telescope during 1978–1984 and results of a new observational program during t...
展开
We present previously unpublished circular polarization (cp) measurements at 4.8 and 8.0 GHz made with the University of Michigan 26-meter prime focus telescope during 1978–1984 and results of a new observational program during the past two years. Based on the preliminary analysis of our recent data, eight sources were detected at 4.8 GHz with average degrees of cp ranging from ≤ 0.1% to ≥ 1%.The results are compared with observations at other frequencies and with linear polarization and total flux density variability in the sources. The behavior of the cp variability observed to date is consistent with stochastic variations produced by mode conversion in transient, opaque emitting regions in the sources. The observed sign changes observed between different epochs and different frequencies are not consistent with the hypothesis that sources maintain a fixed handedness of cp.
收起
摘要 :
Abstract This article presents an ultrathin, broadband, and multipurpose polarization converter design utilizing an anisotropic metasurface for K and Ka band. The proposed polarization converter, which has a single layer F4B as a ...
展开
Abstract This article presents an ultrathin, broadband, and multipurpose polarization converter design utilizing an anisotropic metasurface for K and Ka band. The proposed polarization converter, which has a single layer F4B as a substrate material with hexagonal‐shaped metallic solid structure along with hexagonal ring with diagonal splits on its front surface and a background (a completely metallic surface) on its back, works as not only a circular polarization converter but also a linear polarization to circular polarization (LP to CP) converter. Its polarization conversion rate (PCR) is more than 90% in the frequency range from 17.87 to 43.15 GHz, covering all of the K and Ka bands with a relative bandwidth of 83% under normal incidence case. For incidence angles up to 40°, PCR is observed to be greater than 75% in almost all of the K and Ka bands (except for the frequency range between 24.72 and 27.11 GHz). Furthermore, the proposed design has LP to CP in two different frequency bands, 16.23–16.74 GHz and 48.6–48.8 GHz. The proposed polarization converter, as advantages, is low cost, ultra thin, broadband, and facile, which can be useful in linear cross polarization conversion in K and Ka band applications.
收起
摘要 :
We present a design for a superachromatic circular polarizer that can be constructed with conventional, two-element, achromatic half-wave and quarter-wave retarders and used over the whole range of visible wavelengths.
摘要 :
The possible numbers of optical axes in absorbing triclinic crystals have been considered. Most of these crystals possess four circular optical axes; however, there may be crystals having one isotropic optical axis, two or three c...
展开
The possible numbers of optical axes in absorbing triclinic crystals have been considered. Most of these crystals possess four circular optical axes; however, there may be crystals having one isotropic optical axis, two or three circular optical axes, or simultaneously one isotropic and one or two circular optical axes. It is shown that particular cases significantly differ from the general case of crystal with four circular axes. The dependence of the form of the complex permittivity tensor on the number of optical axes is presented. The ellipticities of eigenwaves and the transmitted-light ellipticity in the case of normal incidence of a wave with a right- or left-hand circular polarization are calculated for these crystals.
收起
摘要 :
An aperture-coupled ring-antenna is presented in this communication. The antenna is fed by a microstrip line through a unique aperture configuration. The aperture contains a square slot ring with four short branch slots protruding...
展开
An aperture-coupled ring-antenna is presented in this communication. The antenna is fed by a microstrip line through a unique aperture configuration. The aperture contains a square slot ring with four short branch slots protruding toward the center of the ring. It is studied that axial-ratio and return-loss bandwidths of 8.7% centered at 2.53 GHz can be achieved. Within 2.42 GHz–2.64 GHz, the gains are all greater than 7 dBic.
收起
摘要 :
In this article, techniques to generate circularly polarized waves for a quad-unit are investigated. The quad-unit is offset-fed by an open rectangular ring. It has been shown that both 3-dB axial ratio and 10-dB return loss bandw...
展开
In this article, techniques to generate circularly polarized waves for a quad-unit are investigated. The quad-unit is offset-fed by an open rectangular ring. It has been shown that both 3-dB axial ratio and 10-dB return loss bandwidths can be achieved up to 11%. With a large ring, we have a stable maximum beam at the bore-sight direction. In experiments, it can provide a gain of 7 dBic at 5.5 GHz.
收起
摘要 :
In this study, a novel, simple single-feed square-ring antenna is proposed for circular polarization (CP) operation. The design procedure involves three stages. In the first step, a conventional square-ring antenna is loaded with ...
展开
In this study, a novel, simple single-feed square-ring antenna is proposed for circular polarization (CP) operation. The design procedure involves three stages. In the first step, a conventional square-ring antenna is loaded with an open gap at specific locations along the square ring. This antenna exhibits two resonance characteristics ( and ) with polarizations orthogonal to each other. This antenna works as a dual-band dual-linear polarized antenna. In the second step, the second resonant frequency () is controlled without varying the first resonant frequency () by embedding a lumped-chip capacitor/inductor in the open gap of the square-ring antenna. Therefore, the antenna has a tunable frequency ratio (). By choosing a suitable lumped element, two proximal resonant frequencies are obtained, and two orthogonal resonant modes with a 90° phase difference are excited. Finally, pure CP is obtained. In the last stage, a lumped element is realized using a distributed element. Numerous prototypes of the proposed antenna are implemented, and their performance is measured. The measurement results show that radiation patterns with good CP characteristics are obtained at the resonant frequencies.
收起
原文获取