Electromagnetic Penetration Through Finite-Length Narrow Slots in Planar Conducting Screens.

摘要

Electromagnetic field penetration through a narrow slot in a planar conducting surface is determined in both the time and frequency domains by integral equation methods. Integral equations are derived and solved numerically for the slot electric field, from which the field that penetrates the slotted surface is subsequently determined. Results obtained via the two methods are compared. The validity of both methods is established by demonstrating close correlation between data obtained from computations and those determined from measurements. The time-domain equation is solved by a scheme incorporating a finite difference approximation for the differential wave operator in the integral equation. This time-domain scheme obviates the need for matrix inversion, thus allowing the solution to be progressively acquired by ''marching in time.'' The frequency-domain integral equation is solved numerically for the slot electric field, or equivalent magnetic current, by a standard technique utilizing a piecewise linear approximation of the unknown and equation enforcement by pulse testing. From knowledge of the equivalent magnetic current, obtained as the solution of the integral equation, the field which penetrates the slot is calculated at various locations for several cases of plane-wave excitation. A narrow slot was cut in a large conducting sheet and an apparatus was fabricated to measure fields. The experimentation was conducted at the Lawrence Livermore National Laboratory on a frequency-domain test range employing a monocone source over a large ground plane. The field was measured at various shadow-side locations for several combinations of excitation and slot length and width. Data were collected for the cases of slots 10 and 15 cm by 1 and 2 mm in the range 0.5 to 10.5 GHz. 13 refs., 74 figs. (ERA citation 13:055851)