An Ultra Wide Band Antenna Design for Indoor Geolocation Applications

In this paper, we present a miniaturized, Ultra Wide Band (UWB) elliptical slot antenna with a circular stub as a tuning element printed on a FR4 substrate with a dielectric constant of 4.4 operating in the frequency range from 2 GHz up to 14 GHz over which the return loss below -10 dB. The antenna is intended to operate in a system designed to assist the visually impaired in indoor navigation utilizing UWB technology. The concentric circular tuning stub is introduced in order to tune and hence improves coupling of the higher-order modes when the electrical path of the slots and tuning stub becomes an integer number of the guide wavelengths surface current distributions are provided at these higher-order modes to demonstrate the working principle, the frequency response of S as well as the radiation patterns in two principal planes at 3.1 GHz, 6.4 11 GHz, 10.6 GHz and 11 GHz. A graded feed design has been developed to improve the matching of the input impedance of the source over the operating bandwidth of interest. The performance of the proposed feed in terms of bandwidth achieved is shown to outperform the conventional rectangular and tapered feed designs reported in the literature. A parametric study has been conducted to identify the critical parameters that affect the performance of the antenna design in terms of tuning, gain and bandwidth. It has been found that for a properly designed graded feed, the most significant geometrical parameter which affects the bandwidth is the slot dimension especially in the higher frequency regime. On the other hand, we have found that the gap between the tuning stub and the slot has no significant effect on the input impedance.