Use of Transmission Line Methods for Antenna Analysis and Wave Propagation

The transmission line method (TLM) is almost ideally suited for computation of wave propagation in the presence of various media as well as to the representation of sources, including antennas. Being a time domain method, it requires few assumption on the shape or frequency of the source waveform. It can handle a variety of interface conditions as well as material properties including lossy media and perfect conductors. Following a brief introduction to the method and its formulation for perfect dielectrics and conductors we discuss the extension of the method for inclusion of lossy dielectrics, placing the method in perspective relative to other time-domain methods suitable for wave propagation and for modeling of antennas. In this paper we chose to emphasize the interaction of antenna fields and conducting grids with particular application to modeling of shielding effects in relatively widely spaced grids. This in turns has application to shielding of MRI signals. A second focus point of the paper is the use of the transmission line method for the design of antenna adaptive arrays including driving coefficients and beam shaping parameters. While we will constrain ourselves to simple linear arrays of dipoles, for which analytical solutions can be used for comparison, the method is fully expandable to any antenna element and array configuration.