Small aperture on a multiconductor transmission line filled with inhomogeneous dielectrics

The penetration of the electromagnetic pulse through a small aperture in the conducting plane is studied, when a multiconductor transmission line is located behind the aperture. The multiconductor transmission line is filled with inhomogeneous dielectric material, so that the propagating modes have different velocities. The aperture is replaced by a pair of electric and magnetic current moments, and the equivalent multiport for the aperture junction is developed. The accuracy of the dipole moment approach is checked by the continuous spectrum approach, and the limits of validity are established.