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One way to find an analytic approximation of the input impedance of thin wire antennas is to make an educated guess of the current distribution, which is then used for the induced electromotive force (EMF) method. This method is frequently described in the literature and yields accurate results. In this article, it is shown that this method can be used to approximate the transmission line reflection coefficient while including high-frequency effects. It is, hence, applicable to smaller wave lengths than the classical transmission line theory. Two general problems are considered: 1) the infinite wire with a lumped impedance above ground and 2) the semi-infinite wire with an arbitrary port configuration above ground. For both configurations, the reflection coefficient is approximated using the induced EMF method. An important intermediate step is to find exact equations that relate the input impedance and the reflection coefficient. The results are compared to an exact solution and an iterative one, which is used in recent publications. It is shown that the induced EMF method is a good alternative to the iterative method. The novelty of this article is the utilization of the induced EMF method for the analytic approximation of the transmission line reflection coefficient and linking the input impedance and the reflection coefficient. [ABSTRACT FROM AUTHOR]

This paper deals with the analytic determination of the current reflection coefficient for a wire above ground. The trajectory of the wire at the wire terminal is arbitrary and the wire is connected to the ground with an impedance. The reflection coefficient is approximated by an iterative approach for the solution of the so-called mixed potential integral equations. The iteration is initialized by the classical transmission line solution. The tangential electric field on the surface of the thin wire corresponding to the classical solution is then used as a distributed source to determine a correction term for the current. By this way, the scattering of the transverse electromagnetic modes at the discontinuity is included. Very good agreement between the analytic solution and a numerical one is observed. It is shown that broadband matching is not possible with a frequency-independent load. The importance of the incorporation of the high-frequency effects is highlighted by the evaluation of the natural frequencies for two specific wire configurations. [ABSTRACT FROM AUTHOR]

The main goal of this paper is the analytic approximation of the singularity expansion method poles of a long finite wire with vertical risers above a perfectly conducting ground. For wavelengths in the same order of magnitude or smaller than the height of the wire above the ground, the classical transmission-line theory is not valid. Therefore, an asymptotic approach is used to approximate the current on the thin wire, which is expressed in terms of current reflection and scattering coefficients. The perturbation theory is used for their analytic calculation. The complex current is analytically approximated and compared to a numerical simulation for illustration purposes. A very good agreement between the analytic approximations and the numerical ones from literature and simulations is observed. [ABSTRACT FROM AUTHOR]