Wideband Monopole Antenna with WLAN(2.4GHz/5GHz) Dual Band-Stop Function

Abstract

In this thesis, a wideband monopole antenna with dual band-stop function for WLAN (2.4 GHz / 5 GHz) is presented. With the recent development of wireless communication technology, wideband systems such as ultra-wideband (UWB) and world interoperability for microwave access (WiMAX) have been studied. For ultra-wideband system, it is necessary to develop ultra-wideband devices such as antenna, LNA, and so on. However, due to the overlap of the currently allocated UWB frequency band (3.1 to 10.6 GHz) with the existing WLAN service (5.15 to 5.825 GHz) band, a wideband antenna with band-stop function is desirable for reducing the possible interference problem. Prior to discussing the details of antennas design, the basic definition and advantage of microstrip feed structure is explained, briefly. After that, following two microstrip feed printed monopole antennas with band-stop characteristic for UWB application are proposed. Firstly, an UWB antenna with band-rejection characteristic is designed. The band-rejection characteristic for 5 GHz WLAN band is achieved by embedding the spur-lines on the ground. With the change of the length of spur-lines, the center frequency of rejection band can be easily adjusted. Secondly, a wideband monopole antenna with dual band-stop function for WLAN(2.4 GHz / 5GHz) is proposed. By cutting off an arched slot from the radiation patch and inserting spur-lines into the ground, the dual band-stop functions for 2.4 GHz and 5 GHz WLAN bands are obtained. The proposed antenna provides good return loss and radiation pattern characteristics in the frequency band of interest.