Input impedance and impedance matching of a dual-cylindrical antenna array

The input impedance of an antenna array that consists of dual-cylindrical units is investigated. In this paper, the antenna array is separated into two parts, the feeding sub-system and the radiant sub-system. Simultaneously, the radiant sub-system is equivalent to an n-port network. Two steps are taken. First, a set of voltage equations is presented according to the transmission line theory, where the voltages, currents, and impedance for each port of network are deduced. Second, the relations between total input impedance and that of each port are given. It is indicated that the input impedance of the antenna can be 50 Ω by moving the two pistons at the ends and changing diameters of inside and outside conductor of coaxial line