Assessment of worst-case receiving antenna characteristics of metallic industrial structures. Part 1: Electrically-small structures

Approaches to the determination of the worst-case available output power or induced voltage in a structure acting as an unintended receiving antenna are presented. Such structures fall into two categories: `electrically-small¿ and `electricallylarge¿, dependent on the size of the structure relative to the wavelength of the incident radiation. Electrically-small structures have simple radiation patterns; their efficiency is very low and is dominated by the ohmic loss resistance. The most realistic canonical model for this case is the loop antenna: an analysis of the relevant characteristics of this is presented, together with experimental corroboration. The results have implications for prediction of the following hazards: ignition of flammable gas mixtures; shock/burn hazards to personnel; initiation of electric detonators.