ANALYSIS OF PLANAR STRIP GEOMETRIES IN A SUBSTRATE-SUPERSTRATE CONFIGURATION

A moment method procedure is used to analyze the behavior of several different configurations consisting of planar strips in a substrate-superstrate geometry. These include the microstrip transmission line, center-fed dipole, the mutual impedance between two dipoles, and the transmission-line coupled dipole. The effects of a superstrate layer are discussed. For the microstrip transmission line, the effect of the superstrate on the line dispersion is demonstrated. For the center-fed dipole, the superstrate effect on the resonant length and input resistance is seen, and simple formulas are given to approximately calculate these quantities. The effect of a superstrate layer on the mutual impedance between two dipoles is then discussed, and it is demonstrated that a superstrate may be used to significantly reduce the mutual impedance for dipoles in an endfire configuration. The effect of a superstrate layer on the coupling between a dipole and transmission line is examined, and the capacitive nature of the coupling is demonstrated.