Harmonic Analysis of an Array Comprised of Two Coupled Directive Antennas

A harmonic analysis is performed and the radiation patterns are deduced for an antenna system comprised of two parallel half-wave dipoles with parasitic directors above a reflecting plane where the mutual interactions of all the elements are considered. This work represents an extension of a previous analysis in which only a single dipole with a director above a reflecting plane was considered [1]. The results illustrate the importance of the radiated interference at the harmonic frequencies that may be introduced when sufficient harmonic power is available at the antenna input. As a criterion to determine the "worst case" situation, the antenna is assumed to be matched and fed with equal power at each of the harmonics. The resultant field patterns show the following characteristics. 1) The presence of the director introduces side lobes at the fundamental frequency in both the meridional and azimuthal planes. These lobes peak at levels of 9 and 14 dB down, respectively, when compared with the density in the forward direction. 2) The higher the harmonic, the smaller the role played by the presence of the directors. At the seventh harmonic a maximum 1.5-dB difference in value exists when compared with the same antenna configuration when the directors are absent. 3) In the meridional plane at the higher harmonics, side lobe densities exist (e.g., at the fifth and seventh harmonics) that are as intense as the power density in the forward direction for the fundamental frequency.