A general overview of the basic electromagnetic phenomena that govern the behavior of the guiding structures in microwave/millimeter-wave integrated circuits (MMICs) is presented. With emphasis on the microstrip lines, the authors discuss the general characteristics exhibited by these guiding structures, including the effect of dispersion and discontinuities. The purposes are to provide a general overview of the basic electromagnetic phenomena that govern the behavior of these strip lines and to provide a brief description of one of the most versatile analytical methods available for treating these structures. The role of electromagnetics is strongly intertwined with the optimal design of microwave/millimeter-wave integrated circuitry. Only through accurate modeling of the field behavior can the circuit response be properly predicted.>

The propagation constant of an electromagnetic wave on a long horizontal thin wire is determined from a modal equation for various situations: an elevated wire; a buried bare wire; a bare wire located in the air-earth interface; and a buried insulated wire. Analytical expressions are derived under the assumption that the height or depth of the wire is much less than the skin depth of the conducting earth and that the angular variation around the wire can be ignored. Although not restrictive in frequency, these conditions are satisfied for extremely low frequency (ELF) and very low frequency (VLF) applications except possibly for deeply buried wires when the effect of the interface is negligible anyway. We show that the propagation constant of a buried bare wire is significantly different from an elevated one for almost all heights of practical interest. When the bare wire is in the interface or buried in close proximity of the earth surface, we find that the square of the wave propagation constant is the average of the squares of the propagation constants in the two media. Of particular interest is the fact that a buried insulated wire has a much smaller propagation constant than a bare wire at the same location. Thus, a horizontal ELF radiating structure, such as the Sanguine antenna, could behave in much the same manner whether it is elevated or located in a buried cylindrical insulating cavity. This conclusion is strictly valid when the length of the structure is small compared with the wavelength of the propagating current in either case, and when adequate grounding of the structure can be achieved.