Study And Design Of Compact Band Notched Ultra-wideband Antenna

In recent years, with the development of Ultra-wideband (UWB) technology, theresearch on UWB antenna has attracted widespread attention. Compared with narrow bandantenna, the UWB antenna not only has wide bandwidth, stable radiation characteristics andhigh radiation efficiency, but has small volume. However, although a large number of UWBantennas own UWB characteristics, most of them are unsuitable for UWB portable instrumentbecause of their large volume; Meanwhile, other narrow frequency bands exist in the UWBfrequency range, such as the wireless local area network (WLAN). UWB signals are weakand easy to be influenced by the WLAN signals in the communication. According to aboveproblems, the paper analyses the miniaturized and band notched technology of UWB antenna.Following major elements:First, in order to reduce the volume of UWB antenna, the paper summarizes the methodsof miniaturization, and presents three kinds of miniaturized UWB antenna: the curved patchUWB microstrip antenna, the UWB wide aperture antenna and the ladder UWB microstripantenna. The curved patch UWB microstrip antenna loads semicircle unite isosceles trapezoidslot structure in the ground to enlarge the low frequency band, and adjusts the radian of thepatch to improve the return loss of the middle and low frequency band; The UWB wideaperture antenna adopts a gradient feeder to realize smooth transition between the patch andthe microstrip, loads a pentagon slot in the patch and introduces a ladder structure in theground to improve the middle and low frequency band characteristics; The ladder UWBmicrostrip antenna changes the distance between the patch and the ground to adjust theresonance point，introduces ladder structure to improve impedance matching. The three kindsof UWB antenna meet UWB characteristics. The UWB wide aperture antenna is the smallestone, which requires high precision in size, production costs is high. The ladder UWBmicrostrip antenna is larger in size, but it is still having the advantages of small size and easyto integrate. It requires low precision in size and low production costs, and thus fit for lotproduction.Second, in order to restrain the interference between UWB and WLAN, a popularmethod is bringing band notched characteristic to the antenna. The paper summarizes the methods of band notched technology, and presents two kinds of band notched UWB antenna:the inverted-U shape band notched UWB antenna and the inverted-furcation shape bandnotched UWB antenna. Both kinds of band notched UWB antenna load slots based on theladder UWB microstrip antenna in the patch to realize the band notched characteristics. Theslot width in the inverted-U shape band notched UWB antenna is0.2mm, in the inverted-furcation shape band notched UWB antenna is1mm, both have the band notchedcharacteristics in5-6GHz. The inverted-furcation shape band notched UWB antenna has theadvantage in terms of cost.Last, the ladder UWB microstrip antenna and the inverted-furcation shape band notchedUWB antenna were made into practicality and tested; two tests meet the UWB characteristicsin most of the UWB frequency range. The measurement and the simulation results of the firstone are in great agreement. The band notched frequency band of the second test result is4.8-6.2GHz, and fit for the band notched characteristics.