Showing papers by "John N. Sahalos published in 2003"

On the electromagnetic scattering of a chaff cloud

Abstract: Scattering characteristics of a chaff are investigated, using a cloud of wire dipoles. The influence of mutual coupling between the dipoles is taken into account. The cloud is studied in terms of the resonant conditions. Algorithms to specify the stochastic distribution of the dipole positions and orientations are constructed. Finally, the possibility of tracing an obscure target behind the cloud is examined.

Numerical approaches for EMI reduction of ICs and PCBs inside metallic enclosures

Abstract: This work presents a numerical approach to the reduction of electromagnetic interference (EMI) from the emissions of ICs and PCBs inside rectangular metallic enclosures The ICs are modeled as small magnetic dipoles. Their interaction with the enclosures is studied with the dyadic Green's functions. The Monte Carlo procedure in conjunction with optimization techniques is used in order to achieve optimal placement configurations for the ICs, by minimizing the electric current density on the metallic walls. The applications of the above approach in PCB design are discussed

A method for the conservative evaluation of safe space around systems with aperture antennas

Abstract: In this work, a novel method is presented, with which the safe space around aperture antennas can be assessed. The basis of this new approach is the approximate similarity of the contours between uniformly and non-uniformly illuminated apertures. The isoparametric contours that result from numerical calculations have to be replaced by envelope contours that fully enclose them, in order to avoid radio frequency hazards. These envelopes were approximated with analytical formulas. Various examples of different apertures are presented, which demonstrate the mode of application and the validity of our method.

On the safety evaluation of the space in the vicinity of an aperture antenna

Abstract: In this paper, the safety evaluation of the space in the vicinity of an aperture antenna is presented. The basis of our consideration is the approximate similarity of the contours between uniformly and nonuniformly illuminated apertures. Using the equivalence of either the gain or the beam width, it was possible to derive the uniform aperture with similar contours to the corresponding nonuniform one. In order to avoid radiofrequency (RF) hazards, instead of the isoparametric contours, their envelopes have been studied. Also, in the case where the exact axial field and the radiation pattern of the aperture are known, the contours can be approximately presented. Several examples with different apertures show the procedure of drawing the contours and explain the validity of our method.

Design of radiation-emission measurements of an air-traffic surveillance radar

Abstract: The current work presents the procedure of designing and carrying out measurements of radiation emission from an air-traffic surveillance radar The system requirements are first given, and then the equipment used is described The steps to determine the operating characteristics of the radar are specified in detail The necessary methods for manual power measurements and calculations are next explained Since the final measurement system was fully automated, its main features (topology, protocol of operation) are also given Finally, some measurement results taken during the initial phase of system operation are presented and discussed