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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 paper, a planar phased array of circular waveguides arranged in an equilateral triangular grid is analyzed, and the boundary value problem is formulated rather generally in terms of a vector two dimensional integral equation for an array of elements that are arranged in a doubly periodic grid along two skewed (nonorthogonal) coordinates.
Abstract: In this work, a planar phased array of circular waveguides arranged in an equilateral triangular grid is analyzed. The boundary value problem is first formulated rather generally in terms of a vector two dimensional integral equation for an array of elements that are arranged in a doubly periodic grid along two skewed (nonorthogonal) coordinates. Dielectric plugs, covers, and loading, as well as thin irises at the aperture, are accounted for in the formulation. Numerical solutions are obtained by using the Ritz-Galerkin method to solve the integral equation. Excellent agreement with experimental measurements using a waveguide simulator is observed. The existence of forced surface wave phenomena in equilateral triangular grid arrays and their strong dependence upon the mode of excitation is also demonstrated. These phenomena are shown to exist at isolated points in the scan coordinates. Reflection characteristics as well as the polarization characteristics of the radiation pattern are illustrated at selected planes of scan for both linear and circular polarization excitation.

61 citations

Journal ArticleDOI
TL;DR: A set of rotation invariant parameters and corresponding orientation parameters, which are explicit functions of the Mueller matrix elements are proposed, which have potential applications for fast analyzing different anisotropy contributions in the media, such as birefringence, dichroism, and their coexistence.
Abstract: Polarization imaging and Mueller polarimetry provide powerful tools for probing the microstructure of complex anisotropic media, which is a core task in material science, biomedical diagnosis and many research fields However, Mueller matrix elements and many polarization parameters are sensitive to the spatial orientation of the sample and experimental configurations, hindering the effectiveness for distinguishing different sources of anisotropies In this paper, we propose a set of rotation invariant parameters and corresponding orientation parameters, which are explicit functions of the Mueller matrix elements They are valid under the condition that the illumination and detection directions are collinear with the rotation axis of the sample More detailed examinations show that these parameters have potential applications for fast analyzing different anisotropy contributions in the media, such as birefringence, dichroism, and their coexistence The conclusions are validated with Monte Carlo simulations and the experimental results of transparent tape samples

61 citations

Journal ArticleDOI
TL;DR: In this paper, the current distribution in a Tokamak was measured from the change of polarization of an electromagnetic wave traversing the plasma, and a simple numerical method was given for calculating the resulting polarization and illustrated by examples.
Abstract: Presents a theoretical development of a proposal for measuring the current distribution in a Tokamak from the change of polarization of an electromagnetic wave traversing the plasma. A simple numerical method is given for calculating the resulting polarization and is illustrated by examples. The effect of the radial variation of toroidal field is discussed. The analytic solution in the form of a series is used to obtain some properties of the output polarization.

61 citations

Journal ArticleDOI
TL;DR: In this paper, a waveguide-fed circularly polarized (CP) antipodal linear, exponential, exponential-logarithmic tapered slot antennas (AL-, E-, EL-TSA) were designed, fabricated, and measured at Ka-band for a comprehensive study.
Abstract: Antipodal curvedly tapered slot antennas (ACTSAs) with different slot profiles are investigated to achieve the optimum circular polarization performance. The profiles of the tapered slots can be determined by different curves, such as linear, exponential, and logarithmic curves. Therefore, the corresponding waveguide-fed circularly polarized (CP) antipodal linear, exponential, exponential-logarithmic tapered slot antennas (AL-, E-, EL-TSA) are designed, fabricated, and measured at Ka-band for a comprehensive study. The optimized AELTSA provides good impedance matching, gain above 10.3 dBi, sidelobe lower than $-15 {\rm dB}$ , low cross-polarization, and left-hand circularly polarized (LHCP) axial ratio (AR) lower than 3 dB, from 28 to 40 GHz. Moreover, a waveguide-fed LHCP antipodal exponential–exponential tapered slot antenna (AEETSA) is designed at 500 GHz and fabricated by silicon micromachining. The radiation characteristics are examined by measurement results of symmetric beams and ARs lower than 1.5 dB, from 490 to 510 GHz.

61 citations

Journal ArticleDOI
TL;DR: In this article, a circular polarization (CP) and mode reconfigurable wideband orbital angular momentum (OAM) patch array antenna is presented, which can be reconfigured between the left hand CP with a mode $l = +1$ and right-hand CP (RHCP) with amode $l= -1$, over the wide impedance bandwidth of 21%.
Abstract: A circular polarization (CP) and mode reconfigurable wideband orbital angular momentum (OAM) patch array antenna is presented. The proposed design is based on a reconfigurable feed network (RFN), a direct current (dc) bias circuit, and a $2 \times 2$ patch array. By changing the dc bias voltages of p-i-n didoes, the operating state of the antenna can be reconfigured between the left-hand CP with a mode $l = +1$ and right-hand CP (RHCP) with a mode $l = -1$ , over the wide impedance bandwidth of 21%. For the two states, the measured peak gains are larger than 5.3 and 5.2 dBi, and the axial ratios in half-power main beam directions are lower than 1.29 and 1.05 dB, respectively. Different from existing OAM antennas, the diversities of polarization, frequency, and mode, as well as the CP with inherently high cross-polarization discrimination are simultaneously integrated in the proposed antenna, which serves as a good basis for improving the capacity and spectral efficiency of radio systems. In addition, the antenna features single-external input port, a simple RFN occupying a small number of diodes, and a compact size of $1.28 \times 1.28 \times 0.07 \lambda _{0}^{3}$ ( $\lambda _{0}$ is the free-space wavelength at center frequency), all of which ease implementation and reduce fabrication cost. Therefore, the proposed antenna is very promising for modern high-speed and large capacity wireless communication systems.

61 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023384
2022821
2021685
2020927
20191,060
2018968