Time and frequency domain study of the propagation in lossy multilayered waveguide and antenna structures based on a rigorous full-wave analysis

Coupled waveguides of arbitrary cross section in a general multilayered medium are analyzed. The losses can be due to the finite conductivity of the waveguides, due to losses in the layers, or due to radiation losses in surface or space leaky waves, as is the case with microstrip antennas. The complex propagation constants and the line-mode impedance matrix associated with fundamental and higher-order eigenmodes propagated along these structures are determined using a full-wave integral equation technique. A generalized high-frequency equivalent transmission line model is constructed, and a frequency-dependent characteristic impedance matrix is derived. This complex matrix is defined in an unambiguous way and can be seen as the input impedance matrix of the infinitely long coupled transmission line structure. A simple example consisting of a thick microstrip with low conductivity ( sigma =100 kS/m) is considered.<>