Design and Implementation of UWB CPW-Fed Planar Monopole Antenna with Dual Band Rejection Characteristics

Abstract

With the development of high-speed switching technology, ultra-wideband (UWB) systems in high-performance wireless technology is receiving more attention. In February 2002, the Federal Communications Commission (FCC) issued a ruling that UWB systems could use an unlicensed frequency band ranging from 3.1 GHz to 10.6 GHz for data commutations, radar, and other applications so long as their radio signals satisfy a set of spectral masks for indoor and outdoor environments (Nie & Chen, 2008; Maeng et al., 2009). However, the design of antennas for UWB applications faces many challenges. Interference is a serious problem for UWB application systems. The rejection of interference with some existing narrowband wireless services, such as IEEE 802.11a (5.15~5.825GHz) wireless local area network (WLAN) systems and IEEE 802.16 (3.3~3.8GHz) World Interoperability for Microwave Access (WiMAX) systems are necessary for UWB application systems. One way to suppress these interfering signals is to use a spatial filter such as a frequency selective surface above the antenna. However, this approach requires too much space. Recently, many UWB antennas have been proposed in an attempt to overcome the interference problem using frequency band rejection design. The most popular approaches for an antenna design with frequency band rejection are embedding slots (Jyoti et al., 2010; Su et al., 2010; Zhang et al., 2010). However, most of these designs have single band-notched characteristics for the rejection of the WLAN band or WiMAX band. Only a few articles addressed the dual or multi-band rejection designs (Abdollahvand et al., 2010; Hassani et al., 2011; Mei et al., 2010; Wei et al., 2011). Obtaining highly efficient band-notch characteristics is a challenging issue. The main problem of the frequency band rejection design is the difficulty of controlling the bandwidth of the notch band in a limited space. Furthermore, strong coupling between two adjacent notch bands is obstacle to achieve efficient dual band-notched UWB antennas. Therefore, an efficient frequency bands rejection of the WLAN band and WiMAX band is difficult to implement for UWB applications. In this chapter, we propose an ultra-wideband coplanar waveguide (CPW)-fed planar monopole antenna with dual band rejection characteristics. The proposed antenna consists of a microstrip patch with U-n slot (Yang, 1999, 2002). It can achieve a wide bandwidth of 3.0~11.0GHz for voltage standing wave ratio (VSWR) of less than 2, with dual band rejection