Investigation Of Broadband Complementary Antenna

With the fast development of mobile communication,in order to work in 2G,3G and LTE systems,the base station antennas need to have a wide work bandwidth.Besides,in the mobile communication system,the antennas need to have good unidirectional radiation pattern.Wideband magnetoelectric dipole has a wide bandwidth and stable radiation pattern,which is a good base station antenna candidate.In this dissertation,investigations on slot antenna and printed dipole are made firstly.Based on these investigations,three linear magnetoelectric dipoles and a dual polarized magnetoelectric dipole with good unidirectional pattern are proposed.Finally,a linear antenna array satisfying for the LTE standard is made based on the dual polarized magnetoelectric dipole.The dissertation is organized as follows:Firstly,three linear magnetoelectric dipoles are designed.The first design is a wideband antenna based on bowtie slot antenna and planar electric dipole,which could work between 1.7GHz and 2.7GHz with a good unidirectional radiation pattern in the whole impedance bandwidth.The second design composes a slot antenna and printed dipole.By designing the feed properly,a wide impedance bandwidth is realized.The measure result shows the relative bandwidth of this antenna is 45.5%and the gain is 8 ±0.5dB.The third design combines an H shaped slot and printed dipole,the experimental result shows the antenna could work between 1.67GHz and 2.73GHz(Si i<-10dB)with a relative impedance bandwidth about 48.2%.Secondly,based on the former linear magnetoelectric dipole,a ±45° dual polarized magnetoelectric dipole is proposed.The cross slot is replaced by a quassi cross slot and two U shaped power dividers with air bridge technology is used to feed the antenna.The simulated and measured result shows,the proposed antenna has a bandwidth 53%(S11<-10dB).In the bandwidth,the gain is 8±0.5dB and the isolation is more than 20dB between the two ports.Finally,an antenna array,which satisfies the 4G LTE standard,is proposed by using the former ±45°dual polarized magnetoelectric dipole as the array cell.The measured result shows,the antenna array could work between 1.65GHz and 2.96GHz(S11<-10dB),the isolation between two ports is more than 20dB and the gain is 17±1dB in the whole operation bandwidth,which satisfies the need of base station antenna.