Papers by Atef Elsherbeni
Symposium on Antenna Technology and Applied Electromagnetics [ANTEM 2000], 2000
Because of the invisible nature of electromagnetic waves, the tasks of analyzing, modeling, and d... more Because of the invisible nature of electromagnetic waves, the tasks of analyzing, modeling, and designing of antennas and microwave devices are less manageable than the design of other types of electronic circuits or devices. Efforts have been focused on building tools for visualizing electromagnetic waves emerging from canonical and simple structures. With lesser success, there are a few modeling tools available for a true analysis of practical EM designs. However, the majority of such available tools are basically commercial in nature and are cost prohibitive to the researchers in the academic environment. This paper provides an overview of several graphical user interfaces (GUIs) developed for electromagnetic computational tools for the finite difference time domain (FDTD) technique. These user interfaces overcome the major difficulties that slow down the EM analysis process. The main tasks of these GUIs are to simplify the process of describing a composite structure to the compu...
2011 XXXth URSI General Assembly and Scientific Symposium, 2011
A set of general purpose two-dimensional single-field finite-difference time-domain updating equa... more A set of general purpose two-dimensional single-field finite-difference time-domain updating equations for solving oblique incidence electromagnetic problems is derived. The traditional FDTD updating equations are based on Maxwell's curl equations whereas the single-field FDTD updating equations are based on the vector wave equation. Performance analyses of the single-field formulation in terms of CPU time and memory requirement are presented along with numerical validation. It was observed that the single-field method is more efficient than the traditional FDTD formulation in terms of speed and memory requirements for oblique incident problems.
2006 12th Biennial IEEE Conference on Electromagnetic Field Computation
In this contribution the use of finite difference frequency domain technique (FDFD) for the calcu... more In this contribution the use of finite difference frequency domain technique (FDFD) for the calculation of electromagnetic scattering from chiral media is presented. The accuracy of the presented formulations has been verified by comparing the FDFD solutions of one and two-dimensional scattering problems to exact or other numerical solutions.
2012 Asia Pacific Microwave Conference Proceedings, 2012
To satisfy the dual-band dual-polarization requirements of satellite communications, this paper p... more To satisfy the dual-band dual-polarization requirements of satellite communications, this paper presents a single layer reflectarray design using a novel dual-frequency phase synthesis method. In this design, a ring-patch structure is used as the reflectarray element, and its phase responses at two center frequencies are synthesized to optimize the reflectarray performanceat two target bands (12.25-12.75 GHz and 14.0-14.5 GHz). The dual-frequency phase synthesis method is illustrated in details, and the designed results show a broadband performance that covers thefrequency range from 12.25-14.5GHz. Index Terms-Reflectarray, broad band.
IEEE Antennas and Propagation Society International Symposium (IEEE Cat. No.02CH37313)
In this paper we present a spatial power combining architecture consisting of several interacting... more In this paper we present a spatial power combining architecture consisting of several interacting printed antenna arrays placed at dielectric interfaces in multilayered waveguide. Narrowband resonant patch and slot antennas used in earlier designs are replaced by tapered meander line antennas and their modifications, in order to increase the frequency bandwidth and efficiency of the system and provide operation in multiple band regimes. The full-wave analysis of the interacting antenna modules presented here is based on the integral equation formulation for induced electric and magnetic surface current dei1sit.y discretized via the method of moments. Magnetic potential dyadic Green's functions are obtained for a multilayered rectangular waveguide.
2005 IEEE Antennas and Propagation Society International Symposium, 2005
Proceedings of the 16th International Symposium on Power Semiconductor Devices & IC's
A bow-tie slot antenna fed by a coplanar waveguide is designed for wideband operation for radar a... more A bow-tie slot antenna fed by a coplanar waveguide is designed for wideband operation for radar applications. The new design exhibits 40% bandwidth with center frequency around 11 GHz. One and two elements are designed analyzed and verification with measurements is presented.
Proceedings. IEEE SoutheastCon 2001 (Cat. No.01CH37208), 2001
For practical bio-electromagnetic applications, such as the interaction of electromagnetic fields... more For practical bio-electromagnetic applications, such as the interaction of electromagnetic fields with human head and body, accurate simulation of biological tissues is a key factor for reliable results. The characteristics of biological tissues are frequency dependent and thus called dispersive materials. For accurate FDTD simulation of biological tissues, a numerical technique is proposed to derive Debye coefficients from the measured frequency-dependent permittivity of different biological tissues, and then a scattered field FDTD formulation is developed for such dispersive media characterized by multi-tenn Debye expressions. The proposed scattered field FDTD formulation is valid for three dimensional analysis of practical EM problems involving combination of dispersive and nondispersive materials. The developed procedure has been verified for different types of biological tissues over a very wide band of frequency (from 30 Hz to 20 GHz). The reflection coefficients of a semiinfinite dispersive media using one, two, and threeterm Debye expersions are computed and compared favorably with the corresponding analyhcal solution. Hence, the accuracy and stability of modeling multi-term Debye dispersive materials using the proposed scattered FDTD formulation is assessed.
Progress In Electromagnetics Research, 2005
A square slot antenna fed by two orthogonal feedlines is designed for dual polarized applications... more A square slot antenna fed by two orthogonal feedlines is designed for dual polarized applications. The presented antenna has not only dual operating band, but also very wide bandwidth. The bandwidth is 18% in the first band and 82% in the second one. It can sever most of wireless communication applications that operate at 0.9, 1.8, 1.9 and 2.4 GHz and require wide band characteristics. The antenna can also produce circular polarization with wideband characteristics. Arrays of this antenna are also designed and presented. 1 Introduction 2 Antenna Geometry and Dimensions 3 One Element Design 4 Antenna Arrays Design 5 Circularly Polarized Antenna Configuration 6 Conclusion References research interests include Electromagnetic Theory, Finite Difference Time Domain Method, Antenna Design, and Phased Arrays.
Encyclopedia of RF and Microwave Engineering, 2005
Progress In Electromagnetics Research B, 2012
Finite-Difference Time-Domain (FDTD) subgridding schemes can significantly improve efficiency of ... more Finite-Difference Time-Domain (FDTD) subgridding schemes can significantly improve efficiency of various electromagnetic circuit simulations. However, numerous subgridding schemes suffer from issues associated with stability, efficiency, and material traverse capability. These issues limit general applicability of FDTD subgridding schemes to realistic problems. Herein, a robust nonuniform subgridding scheme is presented that overcomes those weaknesses. The scheme improves simulation accuracy with the aid of greatly increased stability margin and an optimal interpolation technique. It also improves simulation efficiency by allowing the use of time step factors as close as the Courant-Friedrichs-Lewy (CFL) limit. In addition, latetime stability and general applicability are verified through practical microstrip circuit simulation examples.
2014 IEEE Antennas and Propagation Society International Symposium (APSURSI), 2014
Planar reflectarray antennas with parabolic-torus phase distribution are investigated for high-ga... more Planar reflectarray antennas with parabolic-torus phase distribution are investigated for high-gain beam-scanning applications. Analytical expressions for the reflectarray aperture phase distribution are derived for the generalized offset configuration. A Ka-band planar reflectarray with 30 dB gain and 40 degree scan coverage is demonstrated. The study reveals that planar reflectarrays with parabolic-torus phase distribution show a momentous promise for high-gain beam-scanning.
2009 IEEE Antennas and Propagation Society International Symposium, 2009
Progress In Electromagnetics Research, 2007
A rigorous semi-analytical solution is presented for electromagnetic scattering from an array of ... more A rigorous semi-analytical solution is presented for electromagnetic scattering from an array of parallel-coated circular cylinders of arbitrary radii and positions due to an obliquely incident TM z plane wave excitation. In order to check the validity of this technique, the radar cross-section of a single coated cylinder, a linear array of cylinders, and an arbitrary position array of cylinders are calculated and compared with available data in the literature. Furthermore, the near field is calculated to prove the validity of the boundary conditions on the surface of any cylinder with obliquely incidence wave. As an application, circular metamaterial cylinders are used to show the effect of metamaterial characteristics in altering the forward and backward scattering and in focusing the near field around the objects.
Progress In Electromagnetics Research, 2008
Passive UHF RFID tag consists of a microchip attached directly to an antenna. Proper impedance ma... more Passive UHF RFID tag consists of a microchip attached directly to an antenna. Proper impedance match between the antenna and the chip is crucial in RFID tag design. It directly influences RFID system performance characteristics such as the range of a tag. It is known that an RFID microchip is a nonlinear load whose complex impedance in each state varies with the frequency and the input power. This paper illustrates a proper calculation of the tag power reflection coefficient for maximum power transfer by taking into account of the changing chip impedance versus frequency.
Progress In Electromagnetics Research, 2007
A rigorous semi-analytical solution is presented for electromagnetic scattering from an array of ... more A rigorous semi-analytical solution is presented for electromagnetic scattering from an array of circular cylinders due to an obliquely incident plane wave. The cylinders are illuminated by either TM z or TE z incident plane wave. The solution is based on the application of the boundary conditions on the surface of each cylinder in terms of the local coordinate system of each individual cylinder. The principle of equal volume model is used to represent cylindrical cross-sections by an array of circular cylinders for both dielectric and conductor cases in order to proof the validity of the presented technique.
Microwave and Optical Technology Letters, 2003
performances. Future work will focus on adding the buffer stages (input and output) with a view t... more performances. Future work will focus on adding the buffer stages (input and output) with a view to improving linearity and noise performance.
Microwave and Optical Technology Letters, 2003
A small size antenna is designed for dual-band operation for personal wireless communication syst... more A small size antenna is designed for dual-band operation for personal wireless communication systems. The design is based on a tapered meander slot in a finite size ground plane, with a microstrip feed line at the opposite side of the dielectric substrate. The antenna
Microwave and Optical Technology Letters, 2003
Design of broadband printed antennas, including the finite arrays of interacting patch, U‐strip, ... more Design of broadband printed antennas, including the finite arrays of interacting patch, U‐strip, U‐slot, and meander slot antennas, are presented for applications in waveguide‐based spatial power combiners operating at X‐band. The effect of several antenna design parameters on antenna bandwidth performance is investigated in this paper. The antenna designs presented show significant advantages in their scattering characteristics compared to rectangular patch and slot antennas traditionally used in spatial power combiners. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 411–415, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10778
Journal of Electromagnetic Waves and Applications, 2005
A square slot antenna fed by two orthogonal feedlines is designed for dual polarized applications... more A square slot antenna fed by two orthogonal feedlines is designed for dual polarized applications. The presented antenna has not only a dual operating band, but also a very wide bandwidth. The bandwidth is 91% in the first band and 40% in the second one. It can simultaneously serve most of the modern wireless communication applications that operate at 1.8, 1.9, 2.4, 5.2 and 5.8 GHz and require wideband characteristics. The antenna can also produce circular polarization with wideband characteristics.
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Papers by Atef Elsherbeni