Fast Evaluation Of Green Functions In Layered Media And Its Application

Numerous theoretical and experimental investigations have been applied to electromagnetic scattering and radiation by objects in free space. Although some positive results have been achieved, these approaches do not include the effects of environments, such as grounds, seawater and atmosphere, which have to be taken into account when the objects are very close to grounds.A fast method for electromagnetic scattering and radiation problems pertinent to objects above a lossy ground is presented, and the scattering and radiation fields by grounds are taken into account. In this approach, a new symmetrical form of Green's function is introduced, which can reduce the number of Sommerfeld integrals (SI) involved in the problem. The integration along the steepest paths and leading-order approximations are introduced to evaluate these Sommerfeld integrals, which can greatly accelerate the computation. The radiation of an electric dipole above a lossy ground is computed based on this approach.For modeling wire antennas above a lossy ground, Method of moments (MoM) based on the electric-field integral equation (EFIE) is applied by using sub-domain triangle basis functions and Galerkin method. Effects of lossy ground's parameter on radiation behavoir are also carefully treated. Numerical results show the validity and efficiency of this approach.The rotating object modulation of antenna radiation above a lossy ground is analyzed by using quasi-stationary method, amplitude modulation and frequency spectrum of which is also achieved. Some valuable conclusion is presented for reference.