Article
Engineering, Electrical & Electronic
Fabian T. Faul, Daniel Korthauer, Thomas F. Eibert
Summary: In near-field measurements, correcting for probe influence is crucial for achieving high accuracy, particularly in the field of antenna measurements based on unmanned aerial vehicles. Research shows that modulation caused by rotating rotor blades of UAVs is dependent on probe antenna polarization, spatial separation from the UAV, and rotor rotation speed, but independent of the actual measurement frequency.
IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT
(2021)
Article
Engineering, Electrical & Electronic
Roberta Palmeri, Giada Maria Battaglia, Andrea Francesco Morabito, Tommaso Isernia
Summary: The new approach decomposes the complex 2-D problem into a series of 1-D problems, which are effectively solved using the spectral factorization method to retrieve the 2-D complex field. The technique is assessed in the case of reflector aperture fields.
IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION
(2022)
Article
Mathematics
Yinan Zhang, Guangxue Wang, Yi Leng, Guowen Yu, Shirui Peng
Summary: This paper proposes a near-field array beamforming model with array element position error and uses an improved Newton maximum entropy algorithm to estimate and compensate for phase errors. The simulation results show that the beams formed by this method have lower sidelobe levels and the effectively compensated area of the phase error compensation function can be divided during beam scanning.
Article
Mathematics, Applied
Long Li, Jiansheng Yang, Bo Zhang, Haiwen Zhang
Summary: This paper addresses the inverse problem of reconstructing the location and shape of buried obstacles in a two-layered medium from phaseless far-field data. By using superpositions of two plane waves with different directions as incident fields, a direct imaging algorithm is developed to locate small anomalies and a recursive Newton-type iteration algorithm is proposed to reconstruct extended obstacles. Numerical experiments demonstrate the feasibility of the algorithms despite challenges from limited aperture measurement data and the presence of a two-layered background medium.
Article
Engineering, Electrical & Electronic
Xin Wang, Keisuke Konno, Qiang Chen
Summary: The article proposes a novel source reconstruction method based on an artificial neural network enhanced by eigenmode currents, named ANN-EC, and applied to the diagnosis of array antennas based on phaseless near-field data. This method improves accuracy and is robust to noise by reducing the number of eigenmode currents.
IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION
(2021)
Article
Engineering, Electrical & Electronic
Hong Tang, Cory J. J. Bulger, Tom Rovere, Bowen Zheng, Sensong An, Hang Li, Yunxi Dong, Mohammad Haerinia, Clayton Fowler, Stephen Gonya, Wei Guo, Hualiang Zhang
Summary: A low-profile flexible dual-band quasi-isotropic antenna is developed for UAV applications. The antenna uses a coaxial structure for feeding to reduce the profile. The design is validated through theoretical analysis, numerical simulations, and measurements, showing good agreement. A MIMO system employing the antenna is assembled and deployed on a UAV for ground testing, demonstrating its potential for improving UAV communications.
IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS
(2023)
Article
Chemistry, Analytical
Leonardo C. dos Santos, Edson R. Schlosser, Marcos V. T. Heckler
Summary: This paper introduces a low-cost architecture for beamforming with antenna arrays on UAVs, utilizing beam switching to enhance antenna gain. Electromagnetic modeling of the structure was done with commercial simulator Ansys HFSS, while radiation patterns were synthesized with particle swarm optimization. The performance of the designed feeder, using SMD components and switches, was evaluated through simulations, demonstrating its effectiveness in low-cost production.
Article
Computer Science, Artificial Intelligence
John Hartley, Hubert P. H. Shum, Edmond S. L. Ho, He Wang, Subramanian Ramamoorthy
Summary: Existing studies on formation control for UAVs have not addressed the need for optimum coverage of targets at all times. This paper proposes a new path planning approach called the Flux Guided (FG) method, which generates collision-free trajectories for multiple UAVs while maximizing target coverage. Experimental results show that the FG method outperforms previous work in terms of efficiency.
EXPERT SYSTEMS WITH APPLICATIONS
(2022)
Article
Computer Science, Artificial Intelligence
John Hartley, Hubert P. H. Shum, Edmond S. L. Ho, He Wang, Subramanian Ramamoorthy
Summary: This paper proposes a new path planning approach called the Flux Guided (FG) method, which generates collision-free trajectories for multiple UAVs while maximizing the coverage of target(s). Experimental results further validate that FG generates UAV trajectories 1.5x shorter than previous work.
EXPERT SYSTEMS WITH APPLICATIONS
(2022)
Article
Engineering, Electrical & Electronic
Marco Salucci
Summary: This letter investigates the effect of different far-field (FF) sampling strategies on the reliability and effectiveness of a state-of-the-art array diagnosis method based on a multitask Bayesian compressive sensing (BCS) technique for detecting faulty elements in planar antenna arrays.
MICROWAVE AND OPTICAL TECHNOLOGY LETTERS
(2022)
Article
Engineering, Electrical & Electronic
Alexander Paulus, Thomas F. Eibert
Summary: According to the electromagnetic uniqueness theorem, the radiation behavior of an antenna under test (AUT) can be determined from measurements of its radiated fields on an enclosing surface. However, in practice, measurements in the radiating near-field (NF) use probe antennas of finite size, leading to spatially blurred signals. In this work, the concept of NF far-field transformations (NFFFTs) with full correction of unknown probe antennas is introduced, and different formulations are presented. Simulation and measurement results validate the concept and highlight its limitations, with a focus on the case when AUT and probe are identical.
IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION
(2023)
Article
Mathematics, Applied
Jianli Xiang, Guozheng Yan
Summary: By employing superposition methods with different incident fields, this paper breaks the translation invariance of scattering obstacles and achieves unique determination results for penetrable anisotropic obstacles.
JOURNAL OF MATHEMATICAL ANALYSIS AND APPLICATIONS
(2022)
Article
Environmental Sciences
Xuegang Xing, Zhuanling Yang, Guangqiang Qian, Guanghong Zhou
Summary: This study conducted long-term monitoring of barchan dunes in the Kumtagh Desert in China, analyzing the migration characteristics and shape changes of the dunes. The findings suggest that there are variations in migration across different positions of the dunes, and the measurements at the center of the leeward slope are more accurate in determining the migration distance and direction.
Article
Mathematics
Jianli Xiang, Guozheng Yan
Summary: In this paper, we establish the unique determination result for inverse acoustic scattering of a penetrable obstacle with a general conductive boundary condition by using phaseless far field data at a fixed frequency. By considering different types of superpositions of incident waves, the translation invariance property is broken, allowing for the reconstruction of the location of the underlying scatterers.
ACTA MATHEMATICA SCIENTIA
(2023)
Article
Engineering, Electrical & Electronic
Nicolas Mezieres, Laurent Le Coq, Benjamin Fuchs
Summary: The phaseless characterization of antennas helps reduce the cost and simplify the measurement of radiating systems, particularly at high frequencies. By using appropriate phase retrieval algorithms, the complex near field can be retrieved from the acquisition of the antenna radiated field magnitude only. A two-scan approach combined with Gerchberg-Saxton algorithm has been proven to lead to accurate phase retrievals, and a new strategy of measuring the field magnitude on a single sphere for two antenna positions is proposed for easier implementation in various measurement setups.
IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS
(2022)
Article
Geography, Physical
Maria Garcia-Fernandez, Guillermo Alvarez-Narciandi, Yuri Alvarez Lopez, Fernando Las-Heras Andres
Summary: In recent years, there has been a growing research interest in the development of airborne-based Ground Penetrating Radar (GPR) systems for the safe and fast detection of buried threats such as landmines and Improvised Explosive Devices (IEDs). This contribution focuses on studying the influence of height information in GPR-Synthetic Aperture Radar (GPR-SAR) images, correcting distortion of imaged targets due to small tilting of UWB antennas on board the UAV, and revising SVD filtering techniques. Experimental validations were conducted using different soil characteristics, and significant improvements in detection capabilities were achieved.
ISPRS JOURNAL OF PHOTOGRAMMETRY AND REMOTE SENSING
(2022)
Review
Geochemistry & Geophysics
Yuri Alvarez Lopez, Maria Garcia-Fernandez, Guillermo Alvarez-Narciandi, Fernando Las-Heras Andres
IEEE GEOSCIENCE AND REMOTE SENSING MAGAZINE
(2022)
Article
Materials Science, Multidisciplinary
Humberto Fernandez-Alvarez, Maria Elena de Cos Gomez, Fernando Las-Heras Andres
Summary: This article proposes a new technique to retrieve the constitutive parameters of grounded metamaterials. Previous methods are not suitable for metamaterials as they rely on reflectivity and transmittivity data. The proposed method extracts the constitutive parameters using reflectivity data from two different angles of incident plane wave. The method is applied to a grounded metasurface, explaining interesting phenomena and analyzing its validity range.
APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING
(2022)
Editorial Material
Environmental Sciences
Alberto Najera, Rebeca Ramis, Fernando Las-Heras Andes, Concepcion Garcia-Pardo, Jose I. Alonso, Jesus Gonzalez-Rubio, Antonio Hernando, Javier Lafuente Martinez, Francisco Vargas Marcos
ENVIRONMENTAL RESEARCH
(2022)
Article
Chemistry, Physical
Maria Elena de Cos Gomez, Humberto Fernandez Alvarez, Alicia Florez Berdasco, Fernando Las-Heras Andres
Summary: Three metasurfaces (MTS) are designed to be combined with a series end-fed 1 x 10 array antenna to achieve imaging applications in the millimeter frequency range. The MTS-array combination reduces secondary lobes, increases FTBR, widens operation bandwidth, enhances gain and radiation efficiency, while maintaining the size. The envisioned application is collision avoidance for visually impaired people at a medium-long distance.
Article
Medicine, General & Internal
Janet Pagnozzi, Yuri alvarez, Ignacio Gonzalez-Pinto
Summary: Spain has the highest rates of liver transplantation per million inhabitants in the world, with distinct profiles of donors and recipients in Asturias. This study analyzed liver transplant recipients in Asturias from 2002 to 2017 and found that the most frequent recipient profile was a male patient (mean age 55 years) with alcoholic or viral chronic parenchymal liver disease at the Child C stage. The study also identified the surgical and postoperative characteristics and noted a median survival of 13 years with a 5-year survival probability of 79.3% and a 10-year survival probability of 61.9%.
JOURNAL OF CLINICAL MEDICINE
(2023)
Article
Geochemistry & Geophysics
Maria Garcia-Fernandez, Guillermo Alvarez-Narciandi, Yuri Alvarez Lopez, Fernando Las-Heras
Summary: The usage of unmanned aerial vehicles (UAVs)-based ground penetrating radar (GPR) systems has gained interest due to their advantages over ground-based systems in terms of contactless inspection and capability to reach difficult-to-access areas. Improving the scanning throughput while maintaining imaging capabilities is a challenge for these systems. This contribution presents an array-based GPR-SAR system for subsurface imaging, which significantly improves the scanning throughput and provides enhanced detection capabilities through the coherent combination of all transmitting-receiving channels of the array.
IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING
(2023)
Article
Engineering, Electrical & Electronic
Yuri Alvarez Lopez, Jaime Laviada, Ana Arboleya, Fernando Las-Heras
Summary: Synthetic aperture radar (SAR)-based microwave imaging systems are widely used in various applications. The scanning speed is a crucial factor in SAR imaging systems, and widening the distance between measurements can increase it. However, this causes the presence of grating lobes that degrade the quality of microwave SAR images. To address this issue, a novel methodology is proposed in this study, which incorporates the amplitude and phase of the field radiated by the transmitting and receiving antennas in the backpropagation imaging algorithm. This method exploits the directive pattern of the antennas to reduce the level of grating lobes in SAR images.
IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT
(2023)
Article
Chemistry, Analytical
Yuri Alvarez Lopez, Fernando Las-Heras Andres
Summary: Fourier-based imaging, along with backpropagation algorithms such as delay-and-sum, is widely used in microwave imaging due to its computational efficiency and maintained image resolution. This paper presents a modified version of the Fourier-based algorithm that takes into account the radiation field of the Tx/Rx antennas of the microwave imaging system, aiming to improve accuracy. The impact on the imaged targets is analyzed quantitatively and qualitatively, with performance compared to other aliasing mitigation methods in subsampled microwave imaging scenarios.
Article
Engineering, Electrical & Electronic
Alicia Florez Berdasco, Jaime Laviada, Maria Elena de Cos Gomez, Fernando Las-Heras
Summary: The aim of this article is to evaluate the limitations of wearable antennas in different collision avoidance scenarios for visually impaired individuals. The analysis examines the use of medium distance obstacle detection and short distance imaging techniques utilizing synthetic aperture radar (SAR). Different measurements are conducted to assess the performance of the antennas and identify their main limitations in various test scenarios.
IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT
(2023)
