scholarly journals Frequency-Diverse Holographic Metasurface Antenna for Near-Field Microwave Computational Imaging

2021 ◽  
Vol 8 ◽  
Author(s):  
Jiaqi Han ◽  
Long Li ◽  
Shuncheng Tian ◽  
Xiangjin Ma ◽  
Qiang Feng ◽  
...  
Keyword(s):  
Frequency Domain ◽  
Imaging System ◽  
Near Field ◽  
Horn Antenna ◽  
Computational Imaging ◽  
Simulation Studies ◽  
Field Patterns ◽  
Full Wave ◽  
Imaging Reconstruction ◽  
Iterative Shrinkage

This article presents a holographic metasurface antenna with stochastically distributed surface impedance, which produces randomly frequency-diverse radiation patterns. Low mutual coherence electric field patterns generated by the holographic metasurface antenna can cover the K-band from 18 to 26 GHz with 0.1 GHz intervals. By utilizing the frequency-diverse holographic metasurface (FDHM) antenna, we build a near-field microwave computational imaging system based on reflected signals in the frequency domain. A standard horn antenna is adopted to acquire frequency domain signals radiated from the proposed FDHM antenna. A detail imaging restoration process is presented, and the desired targets are correctly reconstructed using the 81 frequency-diverse patterns through full-wave simulation studies. Compressed sensing technique and iterative shrinkage/thresholding algorithms are applied for the imaging reconstruction. The achieved compressive ratio of this computational imaging system on the physical layer is 30:1.

scholarly journals Polarization-independent anapole response of a trimer-based dielectric metasurface

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Vladimir R. Tuz ◽  
Andrey B. Evlyukhin
Keyword(s):  
Decomposition Method ◽  
Analytical Approach ◽  
Near Field ◽  
Multipole Moments ◽  
Field Patterns ◽  
Dielectric Particles ◽  
Full Wave ◽  
Resonant States ◽  
Theoretical Results ◽  
Polarization Independent

Abstract The phenomenon of anapole has attracted considerable attention in the field of metamaterials as a possible realization of radiationless objects. We comprehensively study this phenomenon in the cluster-based systems of dielectric particles by considering conditions of anapole manifestation in both single trimers of disk-shaped particles and metamaterial composed on such trimers. Our analytical approach is based on the multipole decomposition method and the secondary multipole decomposition technique. They allow us to associate the anapole with the multipole moments of the trimer and the separate multipole moments of its constitutive particles. The manifestation of anapole in a two-dimensional metamaterial (metasurface) is confirmed by checking the resonant states in the reflected field as well as from the electromagnetic near-field patterns obtained from the full-wave numerical simulation. It is demonstrated that the anapole excitation in trimers results in the polarization-independent suppression of reflection with the resonant enhancement of local electromagnetic fields in the metasurface. Finally, experimental verification of the theoretical results is presented and discussed.

scholarly journals Optical Aberration Calibration and Correction of Photographic System Based on Wavefront Coding

Sensors ◽  
2021 ◽  
Vol 21 (12) ◽  
pp. 4011
Author(s):  
Chuanwei Yao ◽  
Yibing Shen
Keyword(s):  
Imaging System ◽  
Optical Design ◽  
Computational Imaging ◽  
Large Field ◽  
Wavefront Aberration ◽  
Imaging Method ◽  
Image Deconvolution ◽  
Pupil Function ◽  
Wavefront Coding ◽  
Blurred Images

The image deconvolution technique can recover potential sharp images from blurred images affected by aberrations. Obtaining the point spread function (PSF) of the imaging system accurately is a prerequisite for robust deconvolution. In this paper, a computational imaging method based on wavefront coding is proposed to reconstruct the wavefront aberration of a photographic system. Firstly, a group of images affected by local aberration is obtained by applying wavefront coding on the optical system’s spectral plane. Then, the PSF is recovered accurately by pupil function synthesis, and finally, the aberration-affected images are recovered by image deconvolution. After aberration correction, the image’s coefficient of variation and mean relative deviation are improved by 60% and 30%, respectively, and the image can reach the limit of resolution of the sensor, as proved by the resolution test board. Meanwhile, the method’s robust anti-noise capability is confirmed through simulation experiments. Through the conversion of the complexity of optical design to a post-processing algorithm, this method offers an economical and efficient strategy for obtaining high-resolution and high-quality images using a simple large-field lens.

Nonradiative subdiffraction near-field patterns using metagratings

2021 ◽  
Vol 118 (13) ◽  
pp. 131105
Author(s):  
Oshri Rabinovich ◽  
Ariel Epstein
Keyword(s):  
Near Field ◽  
Field Patterns

scholarly journals A theoretical and numerical approach for selecting miniaturized antenna topologies on magneto-dielectric substrates

2015 ◽  
Vol 7 (3-4) ◽  
pp. 369-377 ◽  
Author(s):  
Alex Pacini ◽  
Alessandra Costanzo ◽  
Diego Masotti
Keyword(s):  
Near Field ◽  
Dielectric Materials ◽  
Numerical Approach ◽  
Operating Conditions ◽  
Microwave Range ◽  
Dielectric Substrates ◽  
Full Wave ◽  
Miniaturized Antenna ◽  
Wavelength Radiation ◽  
Definition Of

An increasing interest is arising in developing miniaturized antennas in the microwave range. However, even when the adopted antennas dimensions are small compared with the wavelength, radiation performances have to be preserved to keep the system-operating conditions. For this purpose, magneto-dielectric materials are currently exploited as promising substrates, which allows us to reduce antenna dimensions by exploiting both relative permittivity and permeability. In this paper, we address generic antennas in resonant conditions and we develop a general theoretical approach, not based on simplified equivalent models, to establish topologies most suitable for exploiting high permeability and/or high-permittivity substrates, for miniaturization purposes. A novel definition of the region pertaining to the antenna near-field and of the associated field strength is proposed. It is then showed that radiation efficiency and bandwidth can be preserved only by a selected combinations of antenna topologies and substrate characteristics. Indeed, by the proposed independent approach, we confirm that non-dispersive magneto-dielectric materials with relative permeability greater than unit, can be efficiently adopted only by antennas that are mainly represented by equivalent magnetic sources. Conversely, if equivalent electric sources are involved, the antenna performances are significantly degraded. The theoretical results are validated by full-wave numerical simulations of reference topologies.

Ultra-Wide Band Near-Field Imaging System

2007 ◽  
Author(s):  
Anatoliy O. Boryssenko ◽  
Christophe Craeye ◽  
Daniel H. Schaubert
Keyword(s):  
Imaging System ◽  
Near Field ◽  
Wide Band ◽  
Ultra Wide Band ◽  
Near Field Imaging ◽  
Field Imaging

scholarly journals Design and Analysis of a W-Band Metasurface-Based Computational Imaging System

IEEE Access ◽  
2017 ◽  
Vol 5 ◽  
pp. 9911-9918 ◽  
Author(s):  
Tomas Zvolensky ◽  
Jonah N. Gollub ◽  
Daniel L. Marks ◽  
David R. Smith
Keyword(s):  
Imaging System ◽  
Computational Imaging ◽  
W Band

scholarly journals Imaging with Local Speckle Intensity Correlations: Theory and Practice

2021 ◽  
Vol 40 (3) ◽  
pp. 1-22
Author(s):  
Marina Alterman ◽  
Chen Bar ◽  
Ioannis Gkioulekas ◽  
Anat Levin
Keyword(s):  
Near Field ◽  
Biological Tissues ◽  
Computational Imaging ◽  
Theory And Practice ◽  
Fluorescent Imaging ◽  
Light Sources ◽  
Far Field ◽  
Scattering Layer ◽  
Speckle Patterns ◽  
Field Imaging

Recent advances in computational imaging have significantly expanded our ability to image through scattering layers such as biological tissues by exploiting the auto-correlation properties of captured speckle intensity patterns. However, most experimental demonstrations of this capability focus on the far-field imaging setting, where obscured light sources are very far from the scattering layer. By contrast, medical imaging applications such as fluorescent imaging operate in the near-field imaging setting, where sources are inside the scattering layer. We provide a theoretical and experimental study of the similarities and differences between the two settings, highlighting the increased challenges posed by the near-field setting. We then draw insights from this analysis to develop a new algorithm for imaging through scattering that is tailored to the near-field setting by taking advantage of unique properties of speckle patterns formed under this setting, such as their local support. We present a theoretical analysis of the advantages of our algorithm and perform real experiments in both far-field and near-field configurations, showing an order-of magnitude expansion in both the range and the density of the obscured patterns that can be recovered.

Near Field Electromagnetic Scattering Model Studying for Coarse Sea Surface

2013 ◽  
Vol 756-759 ◽  
pp. 4586-4590
Author(s):  
Jun Gu ◽  
Kun Cai ◽  
Zi Chang Liang
Keyword(s):  
Electromagnetic Scattering ◽  
Near Field ◽  
Horn Antenna ◽  
Measured Data ◽  
Sea Surface ◽  
Scattering Coefficient ◽  
Distributed Model ◽  
Echo Signal ◽  
Scattering Model ◽  
Rough Sea

The simulated PM-spectrum fractal sea surfaces and the 3-D near-field distributed model of horn antenna are built, the near-field formulas of KA method are deduced. The near-field scattering coefficient and the Doppler echo signal of rough sea surfaces are calculated, the agreement with measured data proved the correctness and validity of the near-field scattering model.

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