Radiation Characteristics of Antennas Embedded in a Layer with Two- Temperature Electron Population.

摘要

It is well-known that low frequency electromagnetic (EM) signals are heavily attenuated in a medium with dense electron population. If we create in this medium a small population of relatively hot electrons the composite medium then supports low-frequency electrostatic oscillations known as electron acoustic waves (EAW). The dispersion relation of this composite medium shows that it supports EAW in the frequency band where EM signals are cut off. Our primary interest in this report is to study the radiation characteristics of a source current distribution embedded in a half-space of our composite medium. To enable this, we derive the Green's functions for our problem and hence study the radiation characteristics of antennas. When the source signal frequency is below the plasma frequency, only EAW exist in the composite medium, while only EM waves can exist in the free space above. We find that the far-zone radiation fields of any current distribution consist only of theta-polarized waves. We find that in both cases the radiation patterns are skewed towards the horizon. In particular, we find that the radiation pattern of a horizontal dipole has two lobes as opposed to one in the underdense case.