The Incremental Far Field and Degrees of Freedom of the Sinusoidal Current Filament

2007 ◽  
Vol 49 (4) ◽  
pp. 13-21 ◽  
Author(s):  
E.K. Miller
Keyword(s):  
Degrees Of Freedom ◽  
Far Field ◽  
Current Filament ◽  
Sinusoidal Current

scholarly journals Increasing Utilization of Redundant Virtual Array for DOA Estimation Based on Coprime Array

2020 ◽  
Vol 2020 ◽  
pp. 1-7
Author(s):  
Chenghong Zhan ◽  
Guoping Hu ◽  
Zixin Zhang ◽  
Ziang Feng
Keyword(s):  
Parameter Estimation ◽  
High Precision ◽  
Degrees Of Freedom ◽  
Doa Estimation ◽  
Far Field ◽  
Virtual Array ◽  
Previous Algorithm ◽  
Array Structure ◽  
Simulation Results ◽  
Coprime Array

In this paper, we initiated a method to estimate the direction of arrival (DOA) of far-field, narrowband, and incoherent targets using coprime array. First, we proposed a coprime array structure and analysed the distribution of difference coarray (DCA). The degrees of freedom (DOF) of the proposed coprime array became clearer by referring to the DCA conception. However, previous algorithm only uses the continuous virtual array, which causes the virtual array elements in the repeated position being abandoned. Therefore, the paper analyses the distribution of virtual array based on DCA conception and averages the receiving signal on these redundant virtual array elements to increase the utilization of receiving data. As a result, the algorithm has high precision in parameter estimation. Simulation results have shown the superiority of the proposed algorithm.

scholarly journals Exploiting spatiotemporal degrees of freedom for far-field subwavelength focusing using time reversal in fractals

2016 ◽  
Vol 93 (18) ◽  
Author(s):  
Matthieu Dupré ◽  
Fabrice Lemoult ◽  
Mathias Fink ◽  
Geoffroy Lerosey
Keyword(s):  
Time Reversal ◽  
Degrees Of Freedom ◽  
Far Field

RADIATION FROM A CURRENT FILAMENT CLAD BY AN ANISOTROPIC PLASMA SHEATH

1963 ◽  
Vol 41 (6) ◽  
pp. 858-862
Author(s):  
Yujiro Ohba
Keyword(s):  
Radiation Field ◽  
Linear Polarization ◽  
Plasma Sheath ◽  
Anisotropic Plasma ◽  
Far Field ◽  
Direction Parallel ◽  
Current Filament ◽  
Te And Tm Modes ◽  
Elliptically Polarized ◽  
A Current

The radiation field from a plasma-clad filament carrying a current I0 exp (−jkzz + jωt) is calculated. The plasma, which is finite in thickness, is magnetized in the direction parallel to the current filament. The field outside the plasma sheath is expressed by a combination of TE and TM modes, and in general the field is elliptically polarized. The conditions for circular and linear polarization in the far field are related to the thickness of the plasma sheath and the wave constants of the plasma.

scholarly journals Scattered Far-Field Sampling in Multi-Static Multi-Frequency Configuration

Sensors ◽  
2021 ◽  
Vol 21 (14) ◽  
pp. 4724
Author(s):  
Maria Antonia Maisto ◽  
Mehdi Masoodi ◽  
Giovanni Leone ◽  
Raffaele Solimene ◽  
Rocco Pierri
Keyword(s):  
Frequency Domain ◽  
Degrees Of Freedom ◽  
Scattering Problem ◽  
Inverse Scattering Problem ◽  
Sampling Strategy ◽  
Singular Values ◽  
Far Field ◽  
Scattering Operator ◽  
Full Data ◽  
Data Points

This paper deals with an inverse scattering problem under a linearized scattering model for a multi-static/multi-frequency configuration. The focus is on the determination of a sampling strategy that allows the reduction of the number of measurement points and frequencies and at the same time keeping the same achievable performance in the reconstructions as for full data acquisition. For the sake of simplicity, a 2D scalar geometry is addressed, and the scattered far-field data are collected. The relevant scattering operator exhibits a singular value spectrum that abruptly decays (i.e., a step-like behavior) beyond a certain index, which identifies the so-called number of degrees of freedom (NDF) of the problem. Accordingly, the sampling strategy is derived by looking for a discrete finite set of data points for which the arising semi-discrete scattering operator approximation can reproduce the most significant part of the singular spectrum, i.e., the singular values preceding the abrupt decay. To this end, the observation variables are suitably transformed so that Fourier-based arguments can be used. The arising sampling grid returns several data that is close to the NDF. Unfortunately, the resulting data points (in the angle-frequency domain) leading to a complicated measurement configuration which requires collecting the data at different spatial positions for each different frequency. To simplify the measurement configuration, a suboptimal sampling strategy is then proposed which, by an iterative procedure, enforces the sampling points to belong to a rectangular grid in the angle-frequency domain. As a result of this procedure, the overall data points (i.e., the couples angle-frequency) actually increase but the number of different angles and frequencies reduce and lead to a measurement configuration that is more practical to implement. A few numerical examples are included to check the proposed sampling scheme.

scholarly journals Far field superlensing inside biological media through a nanorod lens using spatiotemporal information

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mohamad J. Hajiahmadi ◽  
Reza Faraji-Dana ◽  
Anja K. Skrivervik
Keyword(s):  
Degrees Of Freedom ◽  
Super Resolution ◽  
Poor Performance ◽  
Biological Tissues ◽  
Far Field ◽  
Scattering Media ◽  
Spatiotemporal Information ◽  
Optical Transducers ◽  
Optical Focusing ◽  
Entropy Criterion

AbstractFar field superlensing of light has generated great attention in optical focusing and imaging applications. The capability of metamaterials to convert evanescent waves to propagative waves has led to numerous proposals in this regard. The common drawback of these approaches is their poor performance inside strongly scattering media like biological samples. Here, we use a metamaterial structure made out of aluminum nanorods in conjunction with time-reversal technique to exploit all temporal and spatial degrees of freedom for superlensing. Using broadband optics, we numerically show that this structure can perform focusing inside biological tissues with a resolution of λ/10. Moreover, for the imaging scheme we propose the entropy criterion for the image reconstruction step to reduce the number of required optical transducers. We propose an imaging scenario to reconstruct the spreading pattern of a diffusive material inside a tissue. In this way super-resolution images are obtained.

scholarly journals A Novel Sparse Array for Localization of Mixed Near-Field and Far-Field Sources

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Yinsheng Wang ◽  
WeiJia Cui ◽  
Yuxi Du ◽  
Bin Ba ◽  
Fengtong Mei
Keyword(s):  
Degrees Of Freedom ◽  
Near Field ◽  
Parameters Estimation ◽  
Estimation Accuracy ◽  
Far Field ◽  
Computation Complexity ◽  
Field Source ◽  
One Dimensional ◽  
Range Parameter ◽  
Array Aperture

As we all know, nested array can obtain a larger array aperture and more degrees of freedom using fewer sensors. In this study, we not only designed an enhanced symmetric nested array (ESNA), which achieved more consecutive lags and more unique lags compared with a generalized nested array but also developed a special cumulant matrix, in the case of a given number of sensors, which can automatically generate the largest consecutive lags of the array. First, the direction-of-arrivals (DOAs) of mixed sources are estimated using the special cumulant matrix. Then, we can estimate the range of the near-field source in the mixed source using a one-dimensional spectral search through estimated DOAs, and in the mixed sources, the near-field and far-field sources are classified by bringing in the range parameter. The largest consecutive lags and composition method of ESNA are also given, under a given number of sensors.Our algorithm has moderate computation complexity, which provides a higher resolution and improves the parameters’ estimation accuracy. Numerical simulation results demonstrate that the proposed array showed an outstanding performance under estimation accuracy and resolution ability for both DOA and range estimation compared with existing arrays of the same physical array sensors.

scholarly journals Far-Field Maximal Power Absorption of a Bulging Cylindrical Wave Energy Converter

Energies ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 5499
Author(s):  
Matthieu Ancellin ◽  
Marlène Dong ◽  
Philippe Jean ◽  
Frédéric Dias
Keyword(s):  
Wave Energy ◽  
Degrees Of Freedom ◽  
Horizontal Cylinder ◽  
Cylindrical Wave ◽  
Wave Energy Converter ◽  
Far Field ◽  
Maximal Power ◽  
Energy Converter ◽  
Maximal Absorption ◽  
The Waves

The maximal power that is absorbed by a wave energy converter can be estimated from the far-field behavior of the waves that are radiated by the device. For realistic estimates, constraints must be used to enforce restrictions on the set of admissible motions when deriving the maximal absorption width. This work is dedicated to the numerical computation of the maximal absorption width under constraints for devices with several non-trivial degrees of freedom. In particular, the method is applied to a model of SBM Offshore’s S3 wave energy converter, a bulging horizontal cylinder. The results are compared with a more classical approach, which consists of computing the linear dynamic response of the wave energy converter interacting with the waves. The far-field maximal absorption width can be seen as an upper bound to evaluate what would be the power captured by a perfect control strategy. The method also shows that the absorption width of the S3 wave energy converter is larger for wavelengths that are smaller than the device length. In practice, this means that S3 wave energy converters will be longer than the maximal wavelength to be captured on the targeted production site.

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