Analysis of arbitrary wire antennas above lossy half-space: new efficient image method

Since Sommerfeld published his work [1] on the field of a vertical current element located on the surface of lossy half-space (in 1909), radiation from sources located above lossy half-space has been thoroughly investigated. Exact approaches to this problem lead to the solutions given by semi-infinite integrals of Bessel's functions (e.g., Sommerfeld integrals). Their numerical evaluation requires use of special integration techniques and it's time-consuming. Approximate approaches have also been proposed, valid for a limited range of half-space electrical parameters, a limited domain above soil or a limited range of frequencies. All of the exact and approximate methods dealing with the problem (except reflection-coefficient method) start either from the Sommerfeld solution or from its basic idea (the representation of the actual field by means of planewaves). This paper presents a new approximate method, not linked to the Sommerfeld approach or to the known methods of images. The method is conceptually simple, but it enables very accurate and efficient evaluation of the current distribution along, and the impedance of, arbitrary wire antennas.