IET Optoelectronics (17518768)16(4)pp. 179-187
In this paper, we proposed a new method to realize the rotational freedom of thin-film solar cells. In this method, an array of reconfigurable nano-patches fed by a plasmonic waveguide is integrated inside the solar cell to receive and trap light in the active layer. The reconfigurable nano-antenna is designed to achieve beam steering by bias voltage in the direction of sunlight during the day using 4-Dimethyl-Amino-N-methyl-4-Stilbazolium Tosylate as an active electro-optic material integrated into the plasmonic waveguide. The proposed solar cell is investigated using the finite-difference frequency-domain method and the drift-diffusion equations of COMSOL Multiphysics software at different wavelengths of light and a wide range of angles of incidence for transverse magnetic (TM) and transverse electric (TE) polarizations. The numerical results show increase in the absorption in large wavelengths of sunlight for the thin-film solar cell with nano-antenna, resulting in a short circuit current enhancement of 1.48 and 1.45 for TE and TM polarisations, respectively. Also, another advantage of the proposed reconfigurable structure is maintaining the performance in different angles of incidence, which may open up a new opportunity in solar energy harvesting. © 2022 The Authors. IET Optoelectronics published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology.
Optics Communications (00304018)517
In this paper, we propose a new architecture of reconfigurable spiral nano-antenna utilized for the applications of modulators and switches by tailoring intensity, efficiency, and beam-steering. The property of real-time tuning is realized by DC-bias voltage applied to DAST layer as a lossless optoelectronic material. The proposed nano-antenna, coupled to a quantum emitter, is investigated and optimized using three-dimensional software with the FDFD method and parametric simulation. The numerical results show that altering bias voltage from −10 to 10 V tailors a unidirectional radiation pattern with a gain in the range of 5.54 to 0 dB. It is also shown the proposed array of spiral nano-antenna increases directivity to the 13.5 dB and rotates radiation pattern of the structure, equal as 24Deg using different bias voltages. © 2022 Elsevier B.V.
Electronics (Switzerland) (20799292)8(4)
The authors would like to change the affiliation for second author, Mohammadreza Eskandari, as listed in the original version of the article [1]. The original version incorrectly listed the affiliation for Mohammadreza Eskandari; he was not working in the previous one as a full-time faculty. He was working at the institution temporarily; he is currently doing research in the new institute as a permanent professor. The corrected author list is provided below: Author List and Affiliations: Mehdi Salarkaleji1, *, Mohammadreza Eskandari2, Jimmy Ching-Ming Chen3 and Chung-Tse Michael Wu4 1 Department of Electrical and Computer Engineering, Wayne State University, Detroit, MI 48202, USA 2 Electrical Engineering, University of Shahreza, Shahreza 86149-56841, Iran; mr.eskandari@shahreza.ac.ir 3 Division of Engineering Technology, Wayne State University, Detroit, MI 48202, USA; jcmchen@wayne.edu 4 Department of Electrical and Computer Engineering, Rutgers University, Piscataway, NJ 08854, USA; ctm.wu@rutgers.edu The authors would like to apologize for any inconvenience caused to the readers by these changes. The change does not affect the scientific results. The manuscript will be updated and the original will remain online on the article webpage, with a reference to this Correction. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.
This paper presents a novel approach for linear sampling method (LSM) to conduct remote sensing for radar applications, such as automotive radar sensors, by incorporating frequency mapping antenna array based on metamaterial leaky wave antennas (MTM-LWAs). Unlike traditional LSM using only one single frequency to illuminate in a certain direction, the proposed approach utilizes a frequency scanning MTM antenna array to perform frequency-space mapping over the targeted three dimensional (3D) background that includes unknown objects, resulting in a significantly increased field-of-view (FOV). The information obtained from the frequency-space scanning scheme is then transferred to the LSM analysis to detect the locations and shapes of the unknown objects. The proposed novel frequency scanning scheme in combination with LSM serves as an efficient 3D remote sensing scheme without the use of any phase shifters. © 2017 IEEE.
Electronics (Switzerland) (20799292)6(4)
Metamaterial leaky wave antennas (MTM-LWAs), one kind of frequency scanning antennas, exhibit frequency-space mapping characteristics that can be utilized to obtain a sufficient field of view (FOV) and reconstruct shapes in both remote sensing and microwave imaging. In this article, we utilize MTM-LWAs to conduct a spectrally encoded three-dimensional (3D) microwave tomography and remote sensing that can reconstruct conductive targets with various dimensions. In this novel imaging technique, we employ the linear sampling method (LSM) as a powerful and fast reconstruction approach. Unlike the traditional LSM using only one single frequency to illuminate a fixed direction, the proposed method utilizes a frequency scanning MTM antenna array able to accomplish frequency-space mapping over the targeted 3D background that includes unknown objects. In addition, a novel technique based on a frequency and polarization hybrid method is proposed to improve the shape reconstruction resolution and stability in ill-posed inverse problems. Both simulation and experimental results demonstrate the unique advantages of the proposed LSM using MTM-LWAs with frequency and polarization diversity as an efficient 3D remote sensing and tomography scheme. © 2017 by the authors. Licensee MDPI, Basel, Switzerland.
IEEE MTT-S International Microwave Symposium Digest (0149645X)pp. 1371-1374
The linear sampling method (LSM) is an effective method to detect complicated structures in a short time. In this paper, we develop a novel kind of LSM by means of metamaterial (MTM) leaky wave antennas (LWAs) to conduct spectrally-encoded three-dimensional (3D) microwave tomography that can reconstruct a conductive target with coaxial multi-layer and various diameter cylinders. The unique frequency-space mapping feature of MTM LWAs enables an efficient 3D microwave imaging with a larger field of view compared with conventional LSM approaches that usually operate at one single frequency. Validated through both theoretical analysis and experimental results, the proposed MTM imaging scheme allows us to reconstruct 3D shapes effectively with minimal prior knowledge of the target and computational resources. Furthermore, the measured results verify the proposed imaging method by successfully detecting the unknown targets with different shapes and locations for the MTM LWAs operating at 1.8-3 GHz. © 2017 IEEE.
The linear sampling method (LSM) is a powerful and fast reconstruction approach and has shown capabilities of both remote sensing and tomography imaging in the microwave frequency range. In this paper, we report some recent advances in developing a novel kind of LSM by means of metamaterial (MTM) leaky wave antennas (LWAs) to conduct spectrally-encoded three-dimensional (3D) microwave tomography that can reconstruct a conductive target with coaxial multi-layer and various diameter cylinders. The unique frequency-space mapping feature of MTM LWAs enables an efficient 3D microwave imaging with a larger field of view compared with conventional LSM approaches that usually operate at one single frequency. It is shown that the LSM can also be used to conduct remote sensing for radar applications, such as automotive radar sensors, by incorporating frequency mapping antenna array based on MTM-LWAs. The proposed frequency scanning scheme in combination with the LSM in this article serves as an efficient 3D remote sensing scheme without the use of phase shifters. © 2017 IEEE.
IEEE Transactions on Antennas and Propagation (15582221)64(8)pp. 3554-3564
A modified level-set method (MLSM) is proposed to simultaneously reconstruct the shape and electrical properties of 2-D objects. As a numerical technique, the formal level-set method (LSM) can retrieve the shape and position of objects, using synthetic/measurement data. In general, the constitutive parameters of an object (e.g., its relative complex permittivity) are among the a priori information needed for the LSM. For MLSM, an evolution strategy is proposed to simultaneously calculate both the shape and complex permittivity of a 2-D object. The initial guesses in respect of the complex permittivity and shape of the target object converge on their real values as the cost function is minimized. The cost function is regularized with two penalty terms. To prevent sudden change in the shape of the object, a curvature-based regularization is used. Also, Laplacian regularizer is used to reduce fluctuations in the object's constitutive parameters during the process. Using different synthetic data sets, the capabilities of MLSM in microwave imaging and parameter estimation are evaluated. It is found that, using MLSM, it is possible to completely separate two adjacent objects, separated by a distance of one-fifteenth of a wavelength. The proposed method can retrieve targets of different relative permittivities, with less than 10% error. One interesting feature of this method is its high fidelity in retrieving the immersed one-tenth-wavelength targets in highly contrasting (up to as high as 8:1) domains. In the case of targets with little contrast (10%), the proposed method, with more iterations, can converge on a value, which is 57% more than the actual value. These features are valuable in distinguishing malignant tissue from normal tissue. © 2016 IEEE.
Journal of Electrical Engineering and Technology (19750102)10(1)pp. 308-313
This paper describes a technique for complete identification of a two-dimensional scattering object and multiple objects immersed in air using microwaves where the scatterers are assumed to be a homogenous dielectric medium. The employed technique consists of initially retrieving the shape and position of the scattering object using a linear sampling method and then determining the electric permittivity and conductivity of the scatterer using adjoint sensitivity analysis. Incident waves are assumed to be TM (Transverse Magnetic) plane waves. This inversion algorithm results in high computational speed and efficiency, and it can be generalized for any scatterer structure. Also, this method is robust with respect to noise. The numerical results clearly show that this hybrid approach provides accurate reconstructions of various objects. © The Korean Institute of Electrical Engineers.
Journal of Electromagnetic Waves and Applications (15693937)29(17)pp. 2308-2320
A 2D complete identification algorithm for dielectric and multiple objects immersed in air is presented. The employed technique consists of initially retrieving the shape and position of the scattering object using a linear sampling method and then determining the electric permittivity and conductivity of the scatterer using adjoint sensitivity analysis. This inversion algorithm results in high computational speed and efficiency, and it can be generalized for any scatterer structure. Also, this method is robust with respect to noise. The numerical results clearly show that this hybrid approach provides accurate reconstructions of various objects. © 2015 Taylor & Francis.
IEEE Antennas and Wireless Propagation Letters (15361225)13pp. 289-292
In this letter, the Kirsch's factorization image reconstruction method is validated using an experimental setup for scattered field measurement. In this setup, two standard double-ridged horn antennas working in frequency range of 1-18 GHz, one as a transmitter and the other as a receiver, are used inside an anechoic chamber to collect multistatic scattered fields of a hard target. The transmitter is farther from the target than the receiver. While the transmitter is fixed, the target and receiver are rotated on a turntable. Equivalently, the transmitter and the receiver are evenly rotated on the circular arcs with different radii about a fixed target. The antennas are facing each other so that the receiver does not shadow the target. The hard target is an elongated cylinder with a plus-shape cross section of side 12 cm. Successful imaging shows the validity of the measured multistatic data and the inversion method. © 2014 IEEE.
In this paper, a target shape reconstruction by using electromagnetic wave in resonance region is proposed. A hybrid level set method and linear sampling method used to reconstruction perfectly electric conducting three dimensional scatterer. The Incident plane wave with frequency 300MHz and uniform directional diversity is exploited to illuminate the corresponding scatterer and the scattered field in the far zone helps to retrieve the scatterer with the largest dimension of 6 meters. The numerical result clearly shows that this inversion algorithm provides an automated process to reconstruct shape of scatterers. © 2014 IEEE.
AP-S International Symposium (Digest) (IEEE Antennas and Propagation Society) (15223965)pp. 886-887
A new method based on steepest descent and topology evolution is presented to identify an unknown scatterer shape and physical property. Level set method is modified to not only evolve an arbitrary penetrable object shape but also retrieve its relative dielectric constant. Computation time is significantly reduced and accurate reconstruction is obtained. The method accuracy is illustrated by two examples. © 2014 IEEE.
IEEE Transactions on Antennas and Propagation (15582221)62(10)pp. 5117-5125
A hybrid shape reconstruction algorithm based on the near-field microwave imaging approach is presented. A combination of the linear sampling and level set methods is used to calculate the shape of three-dimensional scatterers in a background region with compact support. In this regard, the dyadic Green's function of the background environment is calculated numerically. Since the discretization of the near-field integral equation in the matrix form is ill conditioned, regularization is used for solving this problem. The Chan-Vese and level set method are used to retrieve the accurate shape. Different imaging examples are presented to show the stability of the method once exposed to the noise. Furthermore, application of the method in through the wall and immersed object imaging is demonstrated. © 2014 IEEE.
AP-S International Symposium (Digest) (IEEE Antennas and Propagation Society) (15223965)pp. 824-825
A hybrid approach is proposed to reconstruct a three dimensional penetrable object using near-field data. Electric dipoles as the sources of incident field and measuring the scattered field in near-field region are considered. The aperture which dipoles are located on is shaped like a finite cylinder. The numerical result clearly shows that this inversion algorithm provides a robust procedure which resists against the effect of random noise. © 2013 IEEE.
Electromagnetics (1532527X)32(6)pp. 362-374
A new hybrid method for a complete identification of multiple scattering two-dimensional objects using microwaves is proposed in this study, where the scatterers are assumed to be separated with different homogenous dielectric mediums. The hybrid approach consists of initially retrieving the shape and the position of the scattering objects using a linear sampling method and then determining the electric permittivity and conductivity of the scatterers using an intelligent and deterministic methodthe so-called adjoint sensitivity analysis. This approach is technically correct and well organized, which results in high computational speed, efficiency, and stability. In addition, the technique can be generalized for any scatterer structure. Numerical results are used to validate the feasibility of the approach proposed. © 2012 Copyright Taylor and Francis Group, LLC.
Inverse Problems (13616420)26(9)
A shape reconstruction method for microwave imaging of perfect electric conductor objects based on contour deformations exploiting the level set method is presented. The calculation of the method of moments impedance matrix in the direct scattering part is done in a single step using the relation of the original and adjoint systems. In the inverse scattering part the fast marching method is used in the re-initialization process which has drastically improved the velocity of the reconstruction. Based on the simulation results the inverse scattering method presented in this paper has proved to be efficient and accurate, giving highly accurate reconstructions in relatively short computational times for single or multiple objects and also in the presence of noise. The accuracy and efficiency of the method suggest that it could usefully be extended to the three-dimensional case. © 2010 IOP Publishing Ltd.
In this paper, a shape reconstruction method for electromagnetic tomography based on contour deformations exploiting level set method is proposed. The algorithm is able to reconstruct the shape of multiple perfect conducting objects in two-dimensions. Incident waves are assumed to be TM (Transverse Magnetic) plane waves. The fast marching method is used in reinitialization process which has drastically improved the velocity of the reconstruction. The numerical results clearly shows that this inversion algorithm provides accurate reconstructions of objects from initial guess. ©2010 IEEE.
In this paper, a shape reconstruction method for electromagnetic tomography based on contour deformations exploiting level set method is proposed. The algorithm is able to reconstruct the shape of multiple perfect conducting objects in two-dimensions. Incident waves are assumed to be TM (Transverse Magnetic) plane waves. The fast marching method is used in reinitialization process which has drastically improved the velocity of the reconstruction. The numerical results clearly shows that this inversion algorithm provides accurate reconstructions of objects from initial guess. ©2009 IEEE.
