3,447 research outputs found
A novel method to assess human population exposure induced by a wireless cellular network
<p>This paper presents a new metric to evaluate electromagnetic exposure induced by wireless cellular networks. This metric takes into account the exposure induced by base station antennas as well as exposure induced by wireless devices to evaluate average global exposure of the population in a specific geographical area. The paper first explains the concept and gives the formulation of the Exposure Index (EI). Then, the EI computation is illustrated through simple phone call scenarios (indoor office, in train) and a complete macro urban data long-term evolution scenario showing how, based on simulations, radio-planning predictions, realistic population statistics, user traffic data, and specific absorption rate calculations can be combined to assess the index.</p
Synthetic Aperture Radar Imaging
Simulation programs are used to locate the positions of the input target points and generate a 2D SAR image with the Range Migration Algorithm. Using the same methodology, we can create a scene geometry using the concept of Point cloud and run the simulation program to generate raw SAR data
A high-precision SAR echo simulation method based on FDTD
Synthetic aperture radar (SAR) echo simulation offers a low-cost and convenient way to obtain high-resolution images of targets, and plays an important role in system design and algorithm validation. Although high frequency approximation simulation is widely used, it is considered to be imprecise when calculating scattering field of fine structures, such as exhaust pipes and groove structures, especially in low frequency band. In this paper, a finite-difference time-domain (FDTD) based method is proposed for high-precision SAR echo simulation. In this method, scattering process of electromagnetic wave is accurately simulated to obtain equivalent electric and magnetic current on the surface of the target. Also, a near-to-far-field transformation is applied to the equivalent electric and magnetic current to calculate the field at the receiving antenna. In this transformation, a waveform forming method is introduced to simulate stripmap SAR echoes. By introducing this method, the usage of FDTD in one single simulation can be greatly reduced. The experiments show that proposed method can significantly improve the efficiency of the simulation while maintaining echo accuracy
On the usage of GRECOSAR, an orbital polarimetric SAR simulator of complex targets, to vessel classification studies
This paper presents a synthetic aperture radar (SAR)
simulator that is able to generate polarimetric SAR (POLSAR)
and polarimetric inverse SAR data of complex targets. It solves
the electromagnetic problem via high-frequency approximations,
such as physical optics and the physical theory of diffraction,
with notable computational efficiency. In principle, any orbital
monostatic sensor working at any band, resolution, and operating
mode can be modeled. To make simulations more realistic, the
target’s bearing and speed are considered, and for the particular
case of vessels, even the translational and rotational movements
induced by the sea state. All these capabilities make the simulator
a powerful tool for supplying large amounts of data with precise
scenario information and for testing future sensor configurations.
In this paper, the usefulness of the simulator on vessel classification
studies is assessed. Several simulated polarimetric images are
presented to analyze the potentialities of coherent target decompositions
for classifying complex geometries, thus basing an operational
algorithm. The limitations highlighted by the results suggest
that other approaches, like POLSAR interferometry, should be
explored.Peer Reviewe
On the usage of GRECOSAR: an orbital polarimetric SAR simulator of complex targets for vessel classification studies
This paper presents a synthetic aperture radar (SAR)
simulator that is able to generate polarimetric SAR (POLSAR)
and polarimetric inverse SAR data of complex targets. It solves
the electromagnetic problem via high-frequency approximations,
such as physical optics and the physical theory of diffraction,
with notable computational efficiency. In principle, any orbital
monostatic sensor working at any band, resolution, and operating
mode can be modeled. To make simulations more realistic, the
target’s bearing and speed are considered, and for the particular
case of vessels, even the translational and rotational movements
induced by the sea state. All these capabilities make the simulator
a powerful tool for supplying large amounts of data with precise
scenario information and for testing future sensor configurations.
In this paper, the usefulness of the simulator on vessel classification
studies is assessed. Several simulated polarimetric images are
presented to analyze the potentialities of coherent target decompositions
for classifying complex geometries, thus basing an operational
algorithm. The limitations highlighted by the results suggest
that other approaches, like POLSAR interferometry, should be
explored.Peer Reviewe
Hardware-Accelerated SAR Simulation with NVIDIA-RTX Technology
Synthetic Aperture Radar (SAR) is a critical sensing technology that is
notably independent of the sensor-to-target distance and has numerous
cross-cutting applications, e.g., target recognition, mapping, surveillance,
oceanography, geology, forestry (biomass, deforestation), disaster monitoring
(volcano eruptions, oil spills, flooding), and infrastructure tracking (urban
growth, structure mapping). SAR uses a high-power antenna to illuminate target
locations with electromagnetic radiation, e.g., 10GHz radio waves, and
illuminated surface backscatter is sensed by the antenna which is then used to
generate images of structures. Real SAR data is difficult and costly to produce
and, for research, lacks a reliable source ground truth. This article proposes
a open source SAR simulator to compute phase histories for arbitrary 3D scenes
using newly available ray-tracing hardware made available commercially through
the NVIDIA's RTX graphics cards series. The OptiX GPU ray tracing library for
NVIDIA GPUs is used to calculate SAR phase histories at unprecedented
computational speeds. The simulation results are validated against existing SAR
simulation code for spotlight SAR illumination of point targets. The
computational performance of this approach provides orders of magnitude speed
increases over CPU simulation. An additional order of magnitude of GPU
acceleration when simulations are run on RTX GPUs which include hardware
specifically to accelerate OptiX ray tracing. The article describes the OptiX
simulator structure, processing framework and calculations that afford
execution on massively parallel GPU computation device. The shortcoming of the
OptiX library's restriction to single precision float representation is
discussed and modifications of sensitive calculations are proposed to reduce
truncation error thereby increasing the simulation accuracy under this
constraint.Comment: 17 pages, 7 figures, Algorithms for Synthetic Aperture Radar Imagery
XXVII, SPIE Defense + Commercial Sensing 202
Region-enhanced passive radar imaging
The authors adapt and apply a recently-developed region-enhanced synthetic aperture radar (SAR) image reconstruction technique to the problem of passive radar imaging. One goal in passive radar imaging is to form images of aircraft using signals transmitted by commercial radio and television stations that are reflected from the objects of interest. This involves reconstructing an image from sparse samples of its Fourier transform. Owing to the sparse nature of the aperture, a conventional image formation approach based on direct Fourier transformation results in quite dramatic artefacts in the image, as compared with the case of active SAR imaging. The regionenhanced image formation method considered is based on an explicit mathematical model of the observation process; hence, information about the nature of the aperture is explicitly taken into account in image formation. Furthermore, this framework allows the incorporation of prior information or constraints about the scene being imaged, which makes it possible to compensate for the limitations of the sparse apertures involved in passive radar imaging. As a result, conventional imaging artefacts, such as sidelobes, can be alleviated. Experimental results using data based on electromagnetic simulations demonstrate that this is a promising strategy for passive radar imaging, exhibiting significant suppression of artefacts, preservation of imaged object features, and robustness to measurement noise
Recent Topics in Electromagnetic Compatibility
Recent Topics in Electromagnetic Compatability discusses several topics in electromagnetic compatibility (EMC) and electromagnetic interference (EMI), including measurements, shielding, emission, interference, biomedical devices, and numerical modeling. Over five sections, chapters address the electromagnetic spectrum of corona discharge, life cycle assessment of flexible electromagnetic shields, EMC requirements for implantable medical devices, analysis and design of absorbers for EMC applications, artificial surfaces, and media for EMC and EMI shielding, and much more
Wearable Communications in 5G: Challenges and Enabling Technologies
As wearable devices become more ingrained in our daily lives, traditional
communication networks primarily designed for human being-oriented applications
are facing tremendous challenges. The upcoming 5G wireless system aims to
support unprecedented high capacity, low latency, and massive connectivity. In
this article, we evaluate key challenges in wearable communications. A
cloud/edge communication architecture that integrates the cloud radio access
network, software defined network, device to device communications, and
cloud/edge technologies is presented. Computation offloading enabled by this
multi-layer communications architecture can offload computation-excessive and
latency-stringent applications to nearby devices through device to device
communications or to nearby edge nodes through cellular or other wireless
technologies. Critical issues faced by wearable communications such as short
battery life, limited computing capability, and stringent latency can be
greatly alleviated by this cloud/edge architecture. Together with the presented
architecture, current transmission and networking technologies, including
non-orthogonal multiple access, mobile edge computing, and energy harvesting,
can greatly enhance the performance of wearable communication in terms of
spectral efficiency, energy efficiency, latency, and connectivity.Comment: This work has been accepted by IEEE Vehicular Technology Magazin
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