| Since the Federal Communications Commission(FCC)allocated the spectrum from 3.1 to 10.6GHz as the civil ultra-wideband(UWB)frequency band,UWB technology has broken out the military and radar remote sensing application limitations and become a research hot for short distance and high data rate civil wireless communication systems.However,there are many narrowband systems sharing their frequency bands with the UWB spectrum,such as the Wi MAX band(3.3-3.6GHz)and WLAN band(5.15-5.35 GHz,5.725-5.825GHz).In order to suppress the electromagnetic interference between the UWB and narrowband systems and effectively utilize the whole UWB spectrum,it is necessary to study UWB antennas with reconfigurable band-notch characteristics.This paper focuses on the UWB antennas with reconfigurable band-notch characteristics.The main contents of this paper are summarized as follows:1.A UWB slot antenna with reconfigurable dual band-notch characteristics is proposed.The UWB operation is realized by employing a hexagonal slot and a tapered-shape feed line with a rectangular stub.An inverted L-shaped parasitic strip is placed beside the feed-line to achieve the band-notch property in the Wi MAX band,and an inverted U-shaped slot is etched on the rectangular stub to obtain the notch-band in the WLAN band.Switch elements are embedded in the parasitic strip and the inverted U-shaped slot,and then the reconfigurable band-notch characteristics are obtained by controlling the ON and OFF states of the switches.The antenna can operate in four modes: UWB mode,two single band-notch modes and a dual band-notch mode.2.A UWB monopole antenna with reconfigurable dual band-notch performance is proposed.The notched radiating patch and a defective ground structure are employed to achieve the UWB operation.The band-notch functions in the Wi MAX and WLAN band are obtained byetching an rectangular open-ended slot on the radiating patch and an inverted U-shaped slot on the ground plane,respectively.Pin diodes are embedded in the open-ended and inverted U-shaped slot,and that the reconfigurable band-notch performance is realized by changing the states of the PIN diodes.The antenna can operate at a UWB mode,two single band-notch modes and a dual band-notch mode.3.A UWB monopole antenna with reconfigurable multi band-notch characteristics is proposed.The notched rectangular patch is employed to improve the impedance bandwidth,and then the UWB operation is realized.The band-notches of 3.3-3.6GHz,5.15-5.35 GHz and 7.25-7.75 GHz are achieved by etching two C-shaped slots on radiating patch and printing a bending strip on the other side of the substrate.By controlling ON and OFF states of diodes embedded in appropriate position of the C-shaped slots and the bending strip,the antenna can operate in eight modes: a UWB mode,three single-band notched modes,three dual-band notched modes and a triple-band notched mode. |
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