Inductance calculations; methods and equations

Methods for calculating the external inductance of parts of a transmission line are compared. The differences and resemblances of these basic methods are discussed. Closed form equations for several structures, as found in the literature, are given. Furthermore, closed form relations for flat rectangular conductors, with holes or slits, different shapes, are developed and compared with results, if available, presented in the literature. We are particularly interested in the effective external inductance of a part of a transmission line because this inductance is the main cause of a ground noise (or drop, shift, lift) voltage, leading to common mode radiation.