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Effective Impedance of Bolt Loads on Narrow Slot Apertures Having Depth

1992; Taylor & Francis; Volume: 6; Issue: 7 Linguagem: Inglês

10.1163/156939392x01507

1569-3937

Larry K. Warne, K. C. Chen,

Advanced Antenna and Metasurface Technologies

Unintentional slot apertures formed at the joints in the outer shell of a system are typically terminated by bolts or rivets. When the slot is narrow (length and wavelength much larger than the slot cross section) the question arises: How can these loads be incorporated into the antenna model for the slot? Impedance loads for the antenna model are derived by considering the difference between the Hallén filamentary feed representation and the true bolt geometry. Simple formulas are derived for the inductance of such loads. The leading order formulas are derived by means of conformal mapping considering only the interior of the slot. A correction resulting from the exterior of the slot is also given. These formulas show (in the case where the bolt or rivet makes contact with the conductors on each side of the width of the slot) that the bolt or rivet may be treated approximately as a short circuit. This follows because the condition that the slot be narrow, required to treat it by means of an antenna model, is also required for the bolt load to approach a short circuit. However, in the case where an annular gap exists around the bolt or rivet in the slot conducting wall, and the length of this annular region (typically the thickness of the metal wall) is much larger than the slot width, the resulting inductance can dominate the bolt load effect and in certain cases make the bolt or rivet act more as an open circuit; bolt or rivet contact impedance can lead to similar results.