Equivalent circuit modeling of monopoles on a small platform

Monopole radiators on finite ground planes may be used as elements of phased array antennas. A part from mutual coupling of array elements, the coupling to the current modes on the ground plane (“chassis modes”) has to be considered. The paper presents an investigation of the excitation of the first two chassis modes by a monopole radiator at two positions on a small rectangular ground plane. The effects of chassis mode excitation in the radiator impedance and radiation patterns are presented as well as the current distributions on the ground plane. A resonator-based equivalent circuit is shown to model closely the full-wave simulations and allowing the calculation of radiation contributions from the radiator and the chassis modes.