his paper presents a new and original approach to computing T the high-frequency radar cross section (RCS) of complex radar targets in real time, using a 3D graphics workstation. The target (typically, an aircraft) is modeled with the I-DEAS solid-modeling software, using a parametric-surface approach. The high-frequency RCS is obtained through Physical Optics (PO), Method of Equivalent Currents (MEC), Physical Theory of Diffraction (PTD), and Impedance Boundary Condition (IBC) techniques.This method is based on a new and original implementation of high-frequency techniques, which we have called "Graphical Electromagnetic Computing (GRECO)." A graphical-processing approach to an image of the target on the workstation screen is used to identify the surfaces of the target, visible from the radar viewpoint, and to obtain the unit normal at each point of these surfaces. High-frequency approximations to RCS prediction are then easily computed from the knowledge of the unit normal at the illuminated surfaces of the target.The image of the target on the workstation screen, to be processed by GRECO, is obtained, in real time, from an I-DEAS geometric model, using the 3D graphics hardware accelerator of the workstation. Therefore, the CPU time for the RCS prediction is spent only on the electromagnetic part of the computation, while the more time-consuming geometric-model manipulations are left to the grqphics hardware. This hybrid, graphic-electromagnetic computing (GRECO) results in real-time RCS prediction for complex radar targets.
A parasitic layer-based multifunctional reconfigurable antenna (MRA) design based on multi-objective genetic algorithm optimization used in conjunction with full-wave EM analysis is presented. The MRA is capable of steering its beam into three different directions simultaneously with polarization reconfigurability having six different modes of operation. The MRA consists of a driven microstrip-fed patch element and a reconfigurable parasitic layer, and is designed to be compatible with IEEE-802.11 WLAN standards (5-6 GHz range). The parasitic layer is placed on top of the driven patch. The upper surface of the parasitic layer has a grid of 5 5 electrically small rectangular-shaped metallic pixels, i.e., reconfigurable parasitic pixel surface. The EM energy from the driven patch element couples to the reconfigurable parasitic pixel surface by mutual coupling. The adjacent pixels are connected/disconnected by means of switching, thereby changing the geometry of pixel surface, which in turn changes the current distribution over the parasitic layer, results in the desired mode of operation in beam direction and polarization. A prototype of the designed MRA has been fabricated on quartz substrate. The results from simulations and measurements agree well indicating 8 dB gain in all modes of operation.Index Terms-Beam steering, full-wave analysis, multi-objective genetic algorithm, reconfigurable antenna.
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