Scientific Journal of Information Engineering June 2013, Volume 3, Issue 3, PP.46-49
Miniaturized CPW-fed Planar Monopole Antenna for Dual-band WLAN Applications Gaoli Ning Department 1, Systems Engineering Division of CALT, Beijing 100076, China Email: gln429@126.com
Abstract A compact and simple design of CPW-fed planar antenna with dual-band operation for wireless local area networks (WLAN) applications is presented. Using a modified fork-shaped radiation element, multiple impedance bandwidths covering 2.4/5.2/5.8 GHz WLAN bands are obtained. In addition, by meandering the middle strip resonating at the lower band, the antenna is significantly miniaturized. The antenna is successfully designed and measured, exhibiting broadband matched impedance, stable and fairly good gain and omni-directional radiation patterns. To the authors’ knowledge, its overall performance is among the state of the art. Keywords: Monopole Antenna; Miniturized; Dual-band
1 INTRODUCTION Recent developments of modern wireless and mobile communications have evoked increasing demands for novel antennas with multi-band operation [1]. For instance, wireless local area networks (WLAN), a viable, cost-effective and high speed data connectivity solution, operate in 2.4-2.48 GHz, 5.15-5.35 GHz and 5.725-5.825 GHz according to the IEEE 802.11b/a/g/n standards. Various kinds of antennas suitable for WLAN applications have been developed. Among these antennas, the printed monopole antennas have particularly received much more interests than others owing to their potential in low profile, easy fabrication, good impedance matching, and dual- or multiband operation [2-6]. However, most of the recently presented dual- or multi-band antenna designs are either complex in structure [2] or large in antenna size [3,4] or have large cross-polarization and poor radiation pattern performance especially at high frequencies for practical applications [4-6]. In this article, a novel coplanar waveguide (CPW)-fed planar fork-like monopole antenna is proposed to achieve dual-band operation, covering the WLAN bands. By meandering the middle strip resonating at 2.4 GHz, the overall antenna is miniaturized. In addition, the proposed antenna is simple in structure and has excellent radiation performance which is omni-directional in the H-plane and close to bidirectional in the E plane within the bands of operation due to the regular distribution of the current on the radiation element. Details of the antenna design and experimental results are presented and discussed.
2 ANTENNA DESIGN The configuration and photograph of the proposed antenna are depicted in Fig.1 and Fig.2, respectively. The antenna has a simple structure by etching it on one side of an inexpensive FR-4 dielectric substrate with relative dielectric constant of 4.4, loss tangent of 0.02, and thickness of 1.6 mm, while the other side is without any metallization. The proposed antenna is composed of the feeder and the radiation element. The radiation element consists of three strips with different lengths, where the meander strip resonates at 2.4 GHz-band (because it has the longest math for the current distribution) and the straight ones operate at 5.2/5.8 GHz-band, respectively. Note that the radiation elements are close to each other so that the coupling exists and the “a quarter wavelength” law doesn’t apply here. The overall size of the antenna is only 27×16 mm2 thanks to the proper meander configuration while good electrical performance is still retained. The coplanar waveguide is adopted as the feeder, which has many advantages such as simple - 46 http://www.sjie.org/