Current Distribution and Input Impedance of a Horizontal Linear Antenna in the Presence of a Layered Region

In this paper, the current distribution and an input impedance of a horizontal linear antenna in the presence of a layered region are investigated both analytically and numerically. In particular, we demonstrate the case of a four-layered region. The wave-number and characteristic impedance of an eccentrically insulated antenna are obtained first. Subsequently, the analytical formula for the current distribution on the antenna in a four-layered region is derived by applying a limiting process. The computational results show that the upper and lower dielectric layers have different effects on the current distribution and input impedance of the antenna. It is also found that the imaginary part of the input impedance as a function of antenna length has two zero points, where the first and second zero points correspond to a half-wavelength antenna (series resonance) and a full-wavelength antenna (parallel resonance), respectively. It is indicated that when the thickness of the dielectric layers or the antenna height changes, variations on the resonance length of the antenna are observed by examining the imaginary part of the input impedance.