Compact Planar Multi-Band Antennas And Ultra-Wideband Antennas

With the rapid development of modern wireless communication technology, some multi-band communication systems appear. For example,the wireless local-area network (WLAN) operate in the band at 2.4/5.2/5.8 GHz (2.400-2.484/5.150-5.350/5.725-5.825 GHz), worldwide interoperability for microwave access(WiMAX) systems operate in the band at 2.5/3.5/5.5 GHz (2.500-2.690/3.400-3.690/5.250-5.850 GHz). Therefore,in order to satisfy these standards,antennas with dual or multi-band become a hot topic.Since the Federal Communications Commission (FCC) first approved rules for the commercial use of ultra-wideband (UWB) in 2002, the implementation of UWB antenna has become a highly competitive topic. Over the designated UWB range, some other narrowband services that already occupy frequencies in the UWB band are existed, such as WLAN operating in the 5.15-5.825 GHz band and WiMAX service from 3.4 to 3.69 GHz. It is desirable to design the UWB antenna with dual notched frequency bands to minimize the potential interferences between UWB system and narrowband systems.According to the research on the implementation technique of multi-band antennas, three dual-band monopole antennas for WLAN/WiMAX applications are presented. The effects of the design parameters on the antennas are described. The implementation of the dual-band operation are also analyzed. These antennas have small sizes. The lower and upper bands of the antennas are able to cover the WLAN 2.4/5.2/5.8 GHz and WiMAX 2.5/3.5/5.5 GHz bands. Moreover, dipole-like radiation pattern over the operating bands are achieved.Based on the implementation of the band-notched technique, three kinds of band-notched UWB slot antennas are proposed. A compact single band-notched UWB slot antenna with assemble notched structure is firstly presented. The assemble structure are able to generate two filtering frequencies, which can be couple together to shape a much sharper notch-band. And then, two kinds of dual band-notch UWB slot antennas are presented. The desired notched band frequencies can be easily achieved by adjusting the total lengths of the band-notch structures. Moreover, by changing the sizes and locations of the notched structures, the rejected bandwidths can be efficiently controlled. These antennas have good omnodirectional radiation patterns.