2011 EMC Directory & Design Guide - Interference Technology

shielding / cables & connectors
Figure 8. Combination of a transmission line (TL) and method of
moments (MoM) code for solving the irradiation problem.
Num e ric a l S o l u t i o n of C o mpl e x EMC Probl e m s
where D=[I 1
(γb) K 1
(γa)-I 1
(γa) K 1
(γb)] and γ=√jωμ(σ+jωε),
while a and b are the inner and outer radius of the shield
respectively. The electrostatic shielding is much greater than
the magnetostatic shielding, and as a result, the transfer
impedance term dominates at low frequencies. This fact has
led many investigators to neglect the transfer admittance
term in EMC coupling problems.
For braided shields as in Figure 7, the model proposed
by Kley [14] is very popular. The coupling mechanism
giving rise to the transfer impedance and admittance are
enhanced, due to the field penetration through the shield
apertures. At low frequencies, the electrostatic shielding of
the braid is much better than the magnetic field shielding
(Y T