Ground Plane Effect on the Multi-band Multiple Ring Monopole Antenna

Abstract

Multi-band and wideband monopole antennas due to their merits such as near omni-directional radiation patterns, simple structure and low cost have attracted a great deal of attention for modern wireless communication systems. Among these are circular disk and multiple ring monopole antennas. The circular disk monopole antenna with a very large impedance bandwidth was introduced in [1] and [2]. In [3] the effect of changing the circular to an elliptical disk was investigated. The microstrip fed monopole disk antenna, which is suitable to connect to printed circuit boards, was presented in [4]. The multi-band multiple ring monopole antenna was introduced in [5] and [6]. This antenna consists of a set of self-similar circular rings that are superimposed to form the antenna. Comparison between the multiple ring monopole antenna characteristics and disk monopole antenna shows that radiation pattern of the multiple ring monopole antenna at higher frequencies is better than the disk monopole antenna. In [7] this antenna was investigated more and the effect of the ellipticity ratio on elliptical multiple ring antenna was proposed. It has been shown that the wider bandwidths can be obtained by decreasing the ellipticity ratio. In this paper the effect of the changing the height from the ground plane perpendicular to the antenna plane and changing the position of the ground plane from perpendicular to parallel to the antenna plane, which leads to the microstrip fed multiple ring monopole antenna, on the multi-band multiple ring monopole antenna are presented. The results show that at higher frequency bands better matching can be obtained for smaller height from the perpendicular ground plane and it does not affect on the lower frequency bands. It is also shown that changing the position of the ground plane from perpendicular to parallel to the antenna plane improves the matching at the first band significantly. The microstrip fed multiple ring antenna can be integrated with printed circuit boards and used in low-profile applications.