Numerical Evaluation of Electromagnetic-wave Penetration at Normal Incidence through an Inhomogeneous-wave Approach

Abstract

Abstract-This paper presents numerical scenarios concerning penetration in a lossy medium that can be obtained by radiating inhomogeneous electromagnetic waves. Former papers approached this problem, both analytically and numerically, finding requirements and limits of the so-called "deeppenetration" condition, which consists of a wave transmitted in a lossy medium having an attenuation vector whose direction forms the angle of ninety degrees with the normal to the separation surface. The deep-penetration condition always requires an oblique incidence, therefore is not practical in many applications. For this reason, we are interested here in finding whether an inhomogeneous wave guarantees larger penetration than the one obtainable with homogeneous waves, even when the incident wave is normal to the separation surface between two media, i.e. when the deep-penetration condition is not satisfied. We are also interested in verifying numerically whether the lossy-prism structure may achieve larger penetration than the one obtainable through traditional leakywave antennas, and we also wish to propose a lossy-prism design more realistic than the one previously presented in the literature.

Verification of the electromagnetic deep-penetration effect in the real world

“…The design of the horn TEM with lossy prism has to deal with several drawbacks. In 19 , an extensive study of the structure has been performed, and in 20 www.nature.com/scientificreports/ model where the lossy prism began exactly where the horn TEM terminated. Here we inserted the horn TEM inside the prism as we noticed that in this way the surface waves at the interface air-lossy prism were limited.…”

“…This approach was introduced in 9 and foresees a primary source (for instance, a horn antenna) radiating a homogeneous wave toward a lossy prism. Once the primary wave has impinged on the prism, the transmitted wave, that travels into the prism, must possess an attenuation vector 10,12 due to the losses in the material, and once it reaches the end of the prism, if the surface is not parallel to the first one, the tangential component of this attenuation vector will be conserved 19,20 , generating another transmitted inhomogeneous wave, this time in the lossless space.…”

“…The HTwLP was proposed in 9 and further investigated in 19,20 . The analysis performed in 19 shows that α 1 of the generated inhomogeneous wave can be improved by increasing the σ of the prism, this comes to a cost since some of the power emitted by the antenna gets dissipated.…”

“…Note that the only hypothesis to achieve those relations is χ prism = π/2 , which leads to (4) In 20 was shown how the HTwLP can be a good candidate for the deep penetration, even if a simple twodimensional model was considered. In this paper, a realistic structure will be investigated.…”