Dual-Port Dual-Wideband Annular Slot Antenna with Stable Unidirectional Pattern

Abstract

This article describes the design of a dual-wideband annular slot antenna. The proposed structure has been optimized to operate in the typical bands of mobile communication systems (0.824-0.960 GHz and 1.710-2.165 GHz). The antenna is designed considering two independent ports with high isolation, one for each operation band, yielding an antenna that exhibits diplexing feature. The final measured results show that the designed antenna exhibits stable radiation pattern over the frequency in both desired bands. The designed antenna has been used to compose a dual-band linear array. Simulation results indicate good performance in both bands for mobile communication systems. Index Terms-dual-band antenna arrays, multi-band antennas, printed antennas, slot antennas. I. INTRODUCTION Dual-band antennas find applications in several areas, such as in mobile communications and satellite navigation systems. The antenna configuration to achieve multiband behavior can be in stacked or coplanar form [1]. Stacked patches have been used in several antenna designs [2]-[5] and have the advantage of allowing broadband or dual-band behavior. The drawback is the need of a multilayer structure for the assembly, which makes the design and fabrication more complex, hence increasing the fabrication costs. Dual-band operation can be achieved as well with coplanar microstrip structures, whereby a canonical patch geometry is generally modified by the inclusion of slots [6]-[12] or by employing fractal-based geometries [13], [14]. Mobile communication is an example of a system based on multi-band operation. A significant number of printed antennas for radio-base stations have been developed and are reported in the literature. The antenna proposed in [15] is a compact dual-feed dual-polarized patch antenna with bands centered at 0.9 GHz and 1.8 GHz. The antenna has a stacked arrangement and its integration into an array is difficult due to the complex feeding system necessary for dual-band operation. Similarly, the antennas presented in [16]-[18] have also a stacked arrangement. They exhibit good performance, but are not well-suited for low-cost solutions. Alternatively to antennas implemented in microstrip configuration, printed slot antennas have been studied and can be assumed as a solution with lower cost compared to the stacked configuration. In [19], a dual-band annular slot antenna has been studied. It exhibits bidirectional pattern and narrow-band behavior, hence it is not