Radiated Interference and Susceptibility Characteristics of Unshielded Lines

Because of relatively large effective radiating area, interface wiring is often a prime source of interference radiation and pickup in electronic systems. This paper presents a technique which allows quantitative prediction of the radiation and susceptibility characteristics of open wires. The technique is particularly well suited to predicting performance in the radiated interference and radiated susceptibility test setups of interference specifications. Babcock and Sagasta presented useful data for the prediction of radiated interference in the test setups of MIL-I-6181D and MIL-I-11748B. Their data, however, did not show the effect of the diameter of the radiating wire, or the effect, in depth, of its height. In addition, their results could not be extended to modified test setups, for example, that of MIL-STD-462. The arrangement of the radiating wire over a ground plane, in typical EMC test setups, suggests the use of an electric dipole model for analysis. Use of this technique in accordance with the approach by Gerry was found to give very conservative results. In order to apply his technique to the problem where the radiating wire and antenna are of dimensions comparable with their separation, several refinements in his approach are required. In particular, it is necessary to represent the wire as an array of dipoles and to average their effect over the length of the receiving antenna.