| With the rapid development of military electronic technology,the electromagnetic environment in various combat carriers in modern warfare is becoming more and more complex,and the combat carriers are becoming more highly integrated with multiple functions.From the perspective of the history of wireless systems,the existing electronic systems still have some problems such as isolation,local errors and lacking ample functions.However,these problems lead to the interferences and difficulties of coordination between systems.Therefore,integrated electronic systems which can be co-ordinated will be the trend.According to the demand of integrated electronic systems,the antenna bandwidth must be wider than before.Thus,an UWB(Ultra-wideband)phased arrays based on tightly coupled elements are proposed to meet all of the demands.This dissertation is focused on UWB with wide-scan angle,high efficiency and low cost.The main contents of this dissertation are shown as follows:First,theory of tightly coupling and the reason why tightly coupled dipole array can work in an ultra-wide frequency band are introduced.In this part,a novel single-linear polarized phased array antenna based on tightly coupled dipole topology is presented.The overall geometry consists of a tightly coupled dipole with an integrated Balun which serves as an impedance transformer fed by a 50Ω coaxial probe.A shorting post,printed under the dipole,and a chock groove on the ground are applied to remove the in-band disastrous resonances.Two dielectric superstrates over the dipole,separated by air gap,are utilized to realize better impedance matching and wide-angle scanning performance.The dimensions of superstrate below are reduced in order to suppress the surface wave propagation.Finally,the simulated results show that the proposed antenna can achieve a 9:1 bandwidth with VSWR < 3 while scanning to ±45o in E and H planes.It is worth mentioning that the resistance materials,which are often used in publications to pay the cost of radiation efficiency for better VSWR,are not applied in the antenna design in this part.In contrast to the single-polarized phased array,the dual-polarized one within the same aperture shows more remarkable performances,such as polarization multiplexing,polarization agility,superior anti-interference ability and high sensitivity of the system.Therefore,we designed a dual-polarized phased array based on the single-polarized oneto improve aperture utilization and system performances.Two optimized dielectric superstrates,separated by air gap,are mounted above the dipoles as a matching layer to improve the impedance matching and wide-angle scanning performances Moreover,some methods such as metallized holes and slanting microstrip line are applied to solve the problems that the orthogonal connection of the polarizing dipoles and the placements of the two coaxial joints.Finally,simulated results show that each polarization the proposed dual-polarized antenna can operate from 2GHz to 18 GHz and achieve a 9:1 bandwidth with VSWR < 3 when scanning up to ±45o in both E and H planes.Similar to the single-linear polarized phased array antenna mentioned above,the resistance materials are also not used,consequently without the price of lower radiation efficiency.At last,according to the technologies applied to optimize performance of antenna in previous parts,a novel low-cost TCDA is proposed in this part.Two methods to decrease the cost are proposed following.Firstly,the traditional WAIM(wide-angle impedance matching)slabs are replaced with single layer of frequency selective surfaces(FSS),integrated with dipole.Furthermore,the resistance materials which are utilized to optimize VSWR are replaced with lumped resistances and microstrip line.Finally,each single-polarized antenna in the proposed dual-polarized antenna can operate from 0.8GHz to 6GHz with VSWR ≤ 3.0 while scanning up to ±45o in both E and H planes.The radiation efficiency of proposed antenna is finally beyond 70%. |
