Mathematical Modeling of Multi-Element Monopole Antennas.

摘要

This research document presents a new theory for the analysis of multi-element antennas which consists of interconnected conductive structure elements of electrically small dimensions. The theory is based on the retarded electromagnet potentials which permit a diakoptic approach to the problem. The antenna is broken up into its individual structure elements. Each element is assumed to be excited, (a) by currents which are impressed at its terminals, i.e. junctions with adjacent elements (current coupling), and (b) by the electric fields of the currents and charges on all the other elements (field coupling). Both excitations are treated independently. Each impressed current produces a 'dominant' current distribution, a characteristic of the element, which can be readily computed. Current coupling is formulated by 'intrinsic' impedance matrices which relate the scalar potentials at the terminals of an element, caused by its dominant current distributions, to the impressed currents of the element. Field coupling produces 'scatter' currents on all the elements, and is formulated by a 'field coupling' matrix which relates the scalar potentials at the terminals, caused by field coupling, to the impressed currents at all the terminals. Intrinsic and 'field coupling' are combined to form the 'complete' impedance matrix of the diakopted antenna. Enforcing continuity of the currents and equality of the scalar potentials at all the interconnections between the elements yields a system of linear equations for the junction currents and the input impedance of the antenna. Current coupling dominates over field coupling.