CPW-FED COMPACT MULTIBAND MONOPOLE ANTENNA FOR WLAN/WIMAX/X-BAND APPLICATION

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Abstract
A CPW-fed compact multiband planar printed monopole antenna for WLAN/WiMAX/X-Band applications is presented in this paper. The structure size of antenna is 0.144λ 0 ×0.176λ 0 ×0.008λ 0. The proposed antenna is composed of three monopole radiators, a microstrip feed line, and the ground with chamfer. With these structures employed, the antenna can generate four different resonances to cover the desired bands while maintaining low profile. The antenna simulation results show four distinct bands from 2.24 to 2.85 GHz, from 3.29 to 4.12 GHz, from 5.13 to 6.24 GHz, and from 6.58 to 8.57 GHz, which cover the entire WLAN bands (2.4-2.484, 5.15-5.35, and 5.725-5.825 GHz), WiMAX bands (2.5-2.69, 3.4-3.69, and 5.25-5.85 GHz), and X-band satellite communication systems (7.25-7.75 and 7.9-8.4 GHz). For verification of simulation results, a prototype of quad-band antenna is designed, fabricated, and tested. The simulated and measured return losses, radiation patterns, and gains are presented. The proposed antenna possesses compact size, simple structure, high gain, and omnidirectional radiation pattern, which make it a suitable candidate used in small/portable WLAN/WiMAX/X-Band devices. 1. INTRODUCTION With the development of multiple wireless communications standards, group of engineers focus their interests on how to design multiband antennas that can be integrated as many standards such as WLAN, WiMAX, and satellite communication as possible into a single wireless terminal device. In order to meet these requirements, various types of promising multiband antenna designs were studied in [1-18]. Planar printed monopole antennas with various structures in [1-3] have become popular candidates in multi-frequency applications for its advantages of low-cost, low-profile, and easy fabrication, whereas the antenna size is relatively large which is not suitable to be installed in mobile wireless terminals. In [4, 5], the antenna only supports dual bands. Triple-band antennas covering the WLAN (2.4/5.2/5.8 GHz) and WiMAX (3.5/5.5 GHz) bands were presented in [6-12]. Although these antennas support triple bands, they cannot fully cover the required bands, which is a common problem of these antennas. In [13], the antenna covers the entire WLAN/WiMAX band, but its low-frequency gain is low and does not support applications in other bands. Although the design of [14-18] supports up to four operating bands, the antenna structure is either complicated, so it is difficult to manufacture, or takes up unnecessary space, resulting in a large size. And these antennas cannot completely cover the required frequency bands. In this paper, a compact quad-band printed monopole antenna is proposed for WLAN/WiMAX/Xband applications. The total size of the proposed monopole antenna is 18 × 22 × 1 mm 3. The proposed planar monopole antenna also provides nearly omnidirectional radiation patterns in H-plane with maximum peak antenna gains of 2.87/3.48/1.82/3.34 dBi across 2.4/3.5/5.8/8 GHz bands, respectively.

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