Several Bendable Wideband Omnidirectional Terminal Antennas

In this paper,The bendable broadband omnidirectional antenna was studied.The method of widening the bandwidth of antenna,such as changing the antenna structure,branch matching and so on,was introduced.The no source impedance matching circuit and the transmission line converter was deeply explored.Based on LC impedance matching circuit and transmission line impedance converter,four bendable broadband omnidirectional terminal antenna was designed.The first one is UHF bendable broadband omnidirectional terminal antenna.It works at 400MHz~678MHz.The antenna type is dipole.The thin-walled copper tube is set as the upper radiator,the gooseneck is set as the lower radiator.So the antenna could be folded easily to achieve all-round communication.The LC matching circuit was used to broaden the bandwidth of the antenna.At the working frequency band,VSWR ? 3 and the maximum gain of the horizontal plane is 1d Bi~1.8d Bi.The second one is VHF/UHF bendable broadband omnidirectional terminal antenna.It works 225MHz~678MHz.On the basis of the first antenna,wider bandwidth is need.Because of low-frequency point decreased,the antenna size increased 15 cm.In order to enhance the portability of the antenna,the upper radiator was made of elastic steel.T-shaped and the p-shaped mixed-matching circuit was used to achieve the broadband characteristics of antenna.At the working band,VSWR?3,the maximum gain of the horizontal plane is 0d Bi~1.5d Bi.Choke balun was set at feed terminal on these two antennas,so they have a good radiation pattern at the bandwidth.The third one is bendable ultra shortwave broadband omnidirectional antenna.They works at 30MHz~88MHz.In order to achieve portability,gooseneck was installed at bottom of the monopole.The elastic steel was set at the upper section of radiator.1:4 transmission line impedance converter was used to broaden bandwidth of antenna.At working bandwidth,VSWR?2.7,and the maximum gain of the horizontal plane is-8.5d Bi~-1.7d Bi.The total length of the antenna is 1.05 m.The fourth one is a 30~512MHz bendable UWB omnidirectional antenna.On the basis of the third antenna research,the 1:1 transmission line transformer was used to achieve the UWB characteristic.In the working frequency band,VSWR?2.3,the maximum gain of the horizontal plane is-12 d Bi~-1.4d Bi.The totallength of antenna is 1.35 m.These four antennas not only have good radiation pattern and gain characteristics,but also can achieve all-round communication,so they can be used in military multimode terminals.