Gonca Cakir

Planar Octagonal-Shaped UWB Antenna With Reduced Radar Cross Section

A novel planar octagonal-shaped antenna with reduced radar cross section (RCS) for ultra-wideband (UWB) applications is designed and demonstrated experimentally. The proposed antenna is modified using the geometrical shaping method in order to get the RCS reduction. This method is based on the subtraction of metal areas which have the minimum current distributions on the surface of printed antenna. Both of the reference and modified octagonal-shaped antennas are operating at 2.5-18 GHz frequency range with %151 fractional bandwidths. The full-wave electromagnetic simulations and laboratory measurements are performed to characterize their RCSs as a function of frequency, radiation patterns and scattering characteristics. The radiation performance of modified antenna is stable and consistent with the reference antenna. Also the results show that the designed UWB antenna has lower RCS compared to the reference antenna. About 10 dBsm RCS reduction is obtained in the whole operation bandwidth. The designed antenna has very large RCS reduction up to 25 dBsm, especially in the low frequency range.

Radar cross section (RCS) modeling and simulation, part 1: a tutorial review of definitions, strategies, and canonical examples

Modeling and simulation strategies for radar cross section (RCS) prediction are reviewed, and a novel FDTD-based virtual RCS prediction tool is introduced in this two-part paper. Part 1 is reserved for a tutorial review. Concepts and definitions related to RCS modeling are outlined. Analytical approaches, i.e., high-frequency asymptotics (HFA), as well as powerful time- and frequency-domain numerical methods, are given. Canonical examples using the finite-difference time-domain (FDTD) Method, the method of moments (MoM), and physical optics (PO) are presented.

A multipurpose FDTD-based two dimensional electromagnetic virtual tool

A novel, multipurpose, FDTD-based two-dimensional electromagnetic virtual tool has been designed and introduced. A variety of electromagnetic problems, including radio wave indoor/outdoor, urban/rural propagation, electromagnetic compatibility, resonators, closed/open periodic structures, and linear and planar arrays of radiators can be simulated. This paper describes the software and its use in electromagnetics courses

Radar Cross Section (RCS) Modeling and Simulation, Part 2: A Novel FDTD-Based RCS Prediction Virtual Tool for the Resonance Regime

A novel FDTD-based virtual radar cross section (RCS) prediction tool is introduced. Characteristic examples using simple three-dimensional structures, as well as more-realistic complex air and surface targets, are presented. The virtual tool automatically constructs a wire-grid model of the structure under investigation. It is therefore also possible to compare FDTD results against MoM-based NEC (Numerical Electromagnetics Code) data. It is shown that this virtual tool can be used for both educational and research purposes.

FDTD Modeling of Electromagnetic Wave Scattering From a Wedge With Perfectly Reflecting Boundaries: Comparisons Against Analytical Models and Calibration

A classical, canonical problem of electromagnetic wave scattering from a nonpenetrable wedge is modeled with the finite-difference time-domain (FDTD) method, and results are calibrated against the analytical reference solution. A novel, numerical multistep diffraction coefficient calculation model is introduced. Comparisons against analytical exact solutions as well as high frequency asymptotic (HFA) techniques such as the uniform theory of diffraction (UTD) and parabolic equation (PE) method are also given.

A Two-Dimensional FDTD-Based Virtual Visualization Tool for Metamnaterial -Wave Interaction [Education Column]

Metamaterials (MTM) have become a major electromagnetic research topic. Initial studies have focused on understanding their electromagnetic properties and interactions. This paper presents a novel virtual tool, MTM-FDTD, for the visualization of electromagnetic wave interacting with different metamaterials. Snapshots from characteristic examples during these interactions are presented. Scenarios with normal and oblique incidences, demonstrating focusing beams in planar metamaterials and the existence of negative refractive angle, respectively, are presented. One beauty of this virtual tool is that video clips of wave-metamaterial interactions may easily be produced.

A novel virtual FDTD-based microstrip circuit design and analysis tool

A novel FDTD-based virtual education/research tool is introduced, and characteristic examples are presented. The beauty of this tool comes from its visualization power, as well as easy-to-use design steps. The tool can be used effectively in microstripA novel FDTD-based virtual education/research tool is introduced, and characteristic examples are presented. The beauty of this tool comes from its visualization power, as well as easy-to-use design steps. The tool can be used effectively in microstrip circuit analysis and design problems

Antenna Calibration for EMC Tests and Measurements

An antenna is calibrated in an open-field test site (OFTS) and/or an anechoic chamber, which facilities themselves need calibration. The procedures for calibrated test sites (CALTS) are given in the CISPR and ANSI/IEEE standards. The characteristic parameter for calibrated test sites is the normalized site attenuation (NSA). Theoretical calculations and practical measurements of normalized site attenuation are first presented. Antenna-factor (AF) and/or absolute-gain measurement methods are then reviewed. Finally, an alternative antenna calibration approach is given in this tutorial.

A novel virtual FDTD-based microstrip circuit design and analysis tool [Education Column]

A novel FDTD-based virtual education/research tool is introduced, and characteristic examples are presented. The beauty of this tool comes from its visualization power, as well as easy-to-use design steps. The tool can be used effectively in microstripA novel FDTD-based virtual education/research tool is introduced, and characteristic examples are presented. The beauty of this tool comes from its visualization power, as well as easy-to-use design steps. The tool can be used effectively in microstrip circuit analysis and design problems

An octagonal shaped ultra wide band antenna with reduced RCS

In this study, an octagonal shaped ultra wide band (UWB) antenna which radiates at 2.5-18 GHz is designed. The designed antenna covering the entire band is assigned for the UWB applications, which is about 150%. The RCS (radar cross section) of the designed antenna is reduced by modifying the physical structure. RCS of the antenna is reduced up to 25 dB. The proposed antenna is fabricated and the experimental results of the radiation performance are in a good agreement with the simulation results.