Quasi-Static Electromagnetic Fields due to Dipole Antennas in Bounded Conducting Media

The electromagnetic fields due to dipole antennas in a bounded conducting medium modeling the sea have been formulated in integral forms and solved with the following techniques: the brute-force numerical-integration method; the modal approach by finding the residues for the integrals; the image-source approach by using the steepest descent method; and the hybrid technique with the combination of the two latter approaches. Quasi-static field approximations can be applied when the loss tangent of the conducting media is very large and the observation distances are small compared to the free-space wavelength. For very long wavelengths or for sufficiently thin layer thickness the normal mode approach is more useful, for shorter wavelength or for thicker layers, the image method is more efficient and accurate, whereas in the intermediate range the hybrid method then becomes necessary. We have also derived closed-form expressions for the fields at zero frequency in an image series expansion form and used Poisson's series to convert this image series into a mode series for the case when both the receiver and transmitter are located at the interface.