Human exposure to the near field of radiobase antennas - a full-wave solution using parallel FDTD

2003 ◽  
Vol 51 (3) ◽  
pp. 935-940 ◽  
Author(s):  
L. Catarinucci ◽  
P. Palazzari ◽  
L. Tarricone
Keyword(s):  
Wave Solution ◽  
Human Exposure ◽  
Near Field ◽  
Full Wave

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.

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.

Multifunctional metasurfaces integrating near-field display and 3D holography

2021 ◽  
Author(s):  
Wenjuan Du ◽  
Zhilang Lou ◽  
Xuesong Chen ◽  
Long Chen ◽  
Dongliang Tang
Keyword(s):  
Near Field ◽  
Three Dimensional ◽  
Optical Field ◽  
Amplitude Control ◽  
3D Images ◽  
Full Wave ◽  
Complex Functions ◽  
Channel Information ◽  
Amplitude Modulator ◽  
Optical Applications

Abstract Metasurfaces have versatile manipulation capabilities in the optical field and provide the possibility of building a compact optical device with various complex functions. They have been regarded as ideal candidates to construct a miniaturized optical system with high density and multi-channel information. In this work, reflective all-metallic multifunctional metasurfaces consisting of aluminum nanorods are designed by simultaneously realizing the near-filed display and three-dimensional (3D) holography. Specifically, in the proposed design, each nanorod acts as a complex amplitude modulator to provide continuous amplitude control and binary phase control. By carefully optimizing the orientations of nanorods, a multifunctional metasurface can be designed to display a near-field grayscale pattern and far-field 3D images simultaneously. Numerical results by a full-wave simulation validate the good performance of the proposed design. The proposed method could provide more degree of freedom to designs of lightweight devices, which could be employed in optical applications, such as the virtual or augmented reality display and anti-counterfeit technology.

Numerical evaluation of a full-wave antenna model for near-field applications

2012 ◽  
Vol 11 (2) ◽  
pp. 155-165 ◽  
Author(s):  
A.P. Tran ◽  
C. Warren ◽  
F. André ◽  
A. Giannopoulos ◽  
S. Lambot
Keyword(s):  
Numerical Evaluation ◽  
Near Field ◽  
Full Wave ◽  
Wave Antenna ◽  
Antenna Model

scholarly journals Frequency Diversity Array for Near-Field Focusing

Electronics ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 958
Author(s):  
Xu Han ◽  
Shuai Ding ◽  
Yongmao Huang ◽  
Yuliang Zhou ◽  
Huan Tang ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Numerical Methods ◽  
Numerical Optimization ◽  
Near Field ◽  
Optimization Method ◽  
Frequency Diversity ◽  
Initial Amplitude ◽  
Full Wave ◽  
Circular Arrays ◽  
Working Frequency

In this study, a numerical optimization method is proposed to achieve the near-field focusing of square arrays and circular arrays. This method introduced the frequency diversity array (FDA) approach to change the initial amplitude and working frequency. By adjusting the working state of each antenna, the field distribution on any plane can be artificially controlled. To analyze the FDA, a mathematical model for the FDA has been built and the model has been optimized by a numerical algorithm. The results of two different kinds of arrays are verified by numerical methods and full-wave simulation.

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