Beam focusing properties of a circular monopole array on finite ground plane

Wire monopole antennas are widely used for wireless mobile communication systems, because of broadband characteristics and simple fabrication method [1-2]. In multipath terrestrial propagation environment, sector beam needs narrow beamwidth with good horizontal gain, so that while switching the beams from sector to sector, least interference between sectors is present [3]. One way to generate the narrow beam is to excite one element of the circular array (Figure 1), while the other elements are kept passive behaving as reflector [4]. This is similar to the corner reflectors, where by adjusting the aperture angle beamwidth and directivity can be controlled [3]. This paper presents the study on beam focusing properties of a circular monopole array on finite ground plane size by exciting more than one monopole element at a time in a six element circular array capable of generating six sector beams. The effect of varying the number of monopole elements in the array, while exciting only one element is discussed, as well. By placing a reflector behind the array further improves the beam focusing performance. For this study, a circular ground plane of radius Rg=1.50λ=30 cm is selected. The design frequency for this study is 1.50 GHz. The simulations are carried out using Finite Element Method (FEM) program, Ansoft's HFSS [5].