Antennas and Propagation

Abstract

Lecture notes are fully based on books, Balanis [1] Kraus et al. [4], and Rao [9]. Some diagrams are directly from the books. These are acknowledged by inserting the citation. Contents 1 Introduction 2 Types of Antennas 3 Radiation Mechanism 4 Current Distribution on a Thin Wire Antenna 9

Radiation of dipoles at the interface of anisotropic low permittivity media

“…The radiation of antennas at the interface of media has been the subject of study over the years [1]- [3]. In [3] the radiation of dipoles placed on an air-dielectric interface was studied and it was found that the radiation mainly occurs inside the dielectric with interesting radiation pattern shapes.…”

“…In [3] the radiation of dipoles placed on an air-dielectric interface was studied and it was found that the radiation mainly occurs inside the dielectric with interesting radiation pattern shapes. The radiation in the air side was mainly mono-polar, and more importantly, it was much weaker than the radiation in the dielectric, with an approximate power ratio of 1 : 3/2 [2].…”

“…In [3], the study was on dipoles at the interfaces of dielectrics, which have permittivity greater than vaccum, r > 1. In this work however, we aim to study the radiation pattern of a dipole at the interface of an air-metamaterial (MTM), in which the metamaterial is a homogenized medium with an effective permitivity lower than free space, < 0 .…”

“…Such material would be classified as an Epsilon Near Zero (ENZ) medium. The motivation here is to obtain the interesting radiation patterns of [3], but in air. The argument for using ENZ is simple.…”

“…By using an ENZ instead of the dielectric, air plays the role of the dielectric in [3]. Therefore those patterns obtained inside the dielectric in [2], [3], should be attainable now in the air side, as air is now acting as the higher permitivity medium compared to the MTM. Aside from the shape, the strength of the radiation is also stronger in air, rather than in the ENZ.…”