Excitation and detection of waves in the FDTD analysis of N-port networks

An FDTD methodology is provided herein that allows for TEM excitation and detection of signals associated with N-port network analysis. The scheme is based upon the numerical solution of Laplace's equation in the context of the standard Yee grid. The invocation of both equivalence and orthogonality of modes principles assures that the TEM mode of interest is both exclusively excited and detected. Electric and magnetic surface currents are employed to render zero backward radiation from the source plane. Orthogonality is utilized at the terminal plane to extract the TEM mode from a multi-mode signal, provided that the spectrum of the guiding structure is discrete. The advantage of this approach is found in the placement of both the terminal and source planes-both can be placed as close to each other and to the network as necessary, thus alleviating the computational and memory burdens of the simulation. Examples pertaining to this methodology include stripline structures and the monopole strip antenna. The microstrip patch antenna is also considered to demonstrate the difficulties associated with the excitation and detection of quasi-TEM signals in the midst of radiation terms.