A Compact Triple Band Antenna for a Wireless USB Dongle

Abstract

A compact monopole antenna possessing triple resonance (f1, f2, f3) characteristics for (USB) dongle applications is presented. The resonance characteristic f1 is determined by the overall length of the antenna. The monopole antenna acts as the main radiator for f3 as well as the coupling feeding structure for the parasitic resonators in f1, f2. The resonance characteristic f2 is achieved by a combination of the capacitance formed by the coupling between the top and bottom parasitic substrate resonators and the inductance generated by a via bridging the two parasitic resonators.Key words: Monopole Antenna, (USB) Dongle Application. This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/ by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Ⅰ. IntroductionBecause of the rapid development of wireless communication technology, recent research has focused on compact multiband antennas. Among these structures, multiband antennas for USB dongles are of particular interest because they are portable and enable the easy exchange of information based on a simple plug and play interface. Accordingly, several triple band antennas for USB dongle applications have been studied [1]～[4]. In [1] and [2], the triple band is formed by a coupling between a monopole antenna and a parasitic resonator positioned on the bottom of the substrate. In [3], in order to cover the 2.4 GHz band, an inverted-F antenna is used; its ground uses two slots, one for the 3.5 GHz band and the other for the 5.5 GHz band. In [4], a structure that has various current paths obtains different resonances through two strips added to a rectangular radiating element fed asymmetrically by a trapezoidal ground plane. However, the size of these structures is not suitable for wireless USB dongle applications. This paper presents a triple band monopole antenna for wireless USB dongle applications. The authors have previously presented a dual-band antenna resonating at 2.4/5.2/5.8 GHz for wireless USB dongle applications [5]. The design of the proposed antenna is based on the structure outlined in [5]. A parasitic resonator in the bottom of the substrate is added to the proposed antenna and is connected to the top parasitic resonator by a via, which enables the 3.5 GHz band for WiMAX service to be added to our previous dual-band (f1, f3) antenna. In addition, because the top parasitic resonator is folded into a P-shape, the size of the proposed antenna is reduced by 50 % compared to the monopole antenna found in [5]. Ⅱ. Antenna GeometryAs Fig. 1(a) shows, the proposed antenna is composed of a monopole antenna and a parasitic radiator. The monopole is bent down to the substrate with the aim of reducing the space occupied by the antenna and effectively controlling the coupling to the parasitic radiator. In addition, the top parasitic resonator is folded into a P-shape...

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