Abstmct-Bulk current injection and field coupling are analytically compared in order to ascertain if current injection tests are adequate for susceptibility assessment of electronic equipment. Transmission line theory is adopted for modelling wiring harnesses, and the equivalence is discussed by comparing the effects that the two kind of excitation techniques produce at line ends. General results are obtained, which are not affected by any assumptions on the equipment under test. It is shown that, from the theoretical point of view, injection by means of two current probes allows equivalence with any radiated plane wave excitation. The equivalence is achieved by controlling the clamp voltage in order to match the incident field characteristics.

The transient simulation of electrically-long low-loss multiconductor interconnects is considered from a practical point of view. The importance of frequencydependent losses in these interconnects is discussed and a simple transmission line characterization procedure allowing for such losses is proposed. The characterization obtained yields simple and efficient interconnect models, that the user can include, without programming, in any simulator accepting differential operators.

tgrivetQpo1ito. it, ScanaveroQpolito. it}This paper presents PULP, a MATLAB-based package for the determination of the per-unit-length parameters for lossless Multiconductor Transmission Lines. The inductance and capacitance matrices are determined by the Finite Element Method for an extended set of practical interest structures. These include cables with circular cross-section and multilayered structures. The package is loaded with an easy-to-use graphical user interface that makes it suitable for the interactive input of the geometry, simulation, and output of the parameters.

Abstnzct -The effect of lightning channel ching on the temporal waveform of the radiated fieldsof the return stroke is modeled. The effect of branching is isolated, and compared to the effect of tortuosity of an unbranched channel.The "fine structure'' of the temporal waveforms observed in experimental measurements of the electromagnetic field radiated by lightning discharge entails both "macroscopic" , almost-isolated irregularities, as well as noise-like jagged high-frequency components. The no macroscopic)' part in some cases may be attributed t o reflections, from ground or other grounding structures, while the highfrequency irregularities have been in the past years recognized t o be related to the irregularities of the discharge channel [ 11.In that paper the analysis was carried out for a three-dimensionally tortuous channel, constituted by straight segments, as detailed and justified therein, and the focus was on the effect of channel tortuosity on the high-frequency part of the radiation field. The effect of channel branching was not considered: preliminary results on this subject have been presented in [3]. Here, we will extend that analysis of the fine structure of the field radiated by a lightning return stroke on a tortuous, lossy, and branched discharge channel; in particular, we will investigate the effect of all the branchings alone, i.e. excluding the contributions to the field that arise from the abrupt change of direction of the channel, that instead constitute the tortuosity contribution to the fine structure of the field. The modelFor the geometrical modeling of the branclwd channel, we have employed a stepped-leader algorithm for the description of channel formation as an intrinsically two-timescale transient phenomenon, with fast advancement of the channel and almost-stationary conditions between two subsequent steps. At each step of the algorithm, the direction of a new length of channel and the probability of branch formation depend on the local (electric) field. This latter is in turn obtained via the solution of the Laplace equation with b~1 1 l~d i \ r~ conditions that include the already-prehent part of the channel. A typical output of this (computer intensive) nunierical procedure is a tree-like branched channel that reveals right-angle turns and branching that are a consequence of the finitedifferences scheme employed in the discretization of the Laplace equation. Therefore, for the sake of radiation analysis, and an "angular smoothing" will be performed on the channel, consisting in averaging two or more subsequent points.In the following, the part of the channel that (011-nects the cloud to ground directly will l)c called "main channel"; the branches can be hierarchically ordered in terms of their origin: primary branches will depart from the main channel, secondary branches will depart from primary, and so forth.The current on the channel is obtained using an adaptation of the so-called modified transmission line ( M T L ) approximation described in [2]; the 0 -7803 -3608 -9 * 49...

This work presents a model of a tortuous lightning channel, and a study of the consequent electromagnetic coupling to a transmission line. We analyse the fractal dimension of the induced current on the line, compared with the fractal dimension of the lightning channel and the impinging electromagnetic field on the line. This comparison confirms our previous studies pointing out that the channel fractal dimension and the electromagnetic field fractal dimension are related (in particular, for typical lightning parameters they are the same). A comparison of simulated fields and line currents with experimental measurements is also attempted.