Creating Band-Notched Characteristics for Compact UWB Monopole Antennas

In 2002, the FCC in the US authorized the unlicensed use of the ultrawideband (UWB) frequency spectrum for commercial applications in the range from 3.1 to 10.6 GHz with an emission limit of -41.3 dBm/MHz which is near to the thermal noise floor [1]. UWB communication systems operating in such a wide frequency band and low power emission level could easily be interfered by the existing nearby communication systems such as the Wireless Local Area Networks (WLANs) operating in the frequency bands of 2.45-GHz (2.4– 2.484 GHz), 5.25-GHz (5.15–5.35 GHz) and 5.75-GHz (5.725–5.825 GHz) [2] and the Worldwide Interoperability for Microwave Access (WiMAX) systems operating in the 2.35GHz (2.3-2.4 GHz), 2.6-GHz (2.5–2.69 GHz), 3.35-GHz (3.3-3.4 GHz), 3.5-GHz (3.4–3.6 GHz), 3.7-GHz (3.6-3.8 GHz) and 5.8-GHz (5.725–5.85 GHz) bands[3]. Many countries such as the UK, Canada, France, Germany, Argentina and India etc. will allow at least four of these bands in operations [3]. In such cases, the UWB systems could be affected by several interference signals. These interference signal could be suppressed by using RF filtering.