Research And Design Of Broadband Antenna Arrays

With the rapid development of wireless technology and 5G communication applications,the number of wireless terminal devices is increasing rapidly,which puts forward new requirements for the communication system.On the one hand,in order to effectively improve the communication rate and increase the communication capacity,ultra-wideband communication is widely used.As the front-end of UWB communication system,UWB antenna plays a vital role,so the exploration and research of UWB antenna has become an inevitable trend.On the other hand,compared with isolated single antennas,array antennas are easier to realize the functions of beamforming,beam scanning and high gain,which can meet more needs of communication systems,so it has been widely used in wireless communication,navigation,radar and other modern communication systems.This paper focuses on the design of ultra-wideband phased array antenna,which mainly includes the following contents:1.A Vivaldi antenna unit with traditional graded slot structure is designed,the unit cell achieves over 10 times bandwidth in simulation,and the standing wave ratio in the frequency band is less than 2.Then,in order to further optimize the VSWR and antenna gain level,a double antipodal Vivaldi antenna element with VSWR less than 1.5 in the band of 4.07GHz-31.59GHz is designed,and the bandwidth can reache 12.3 times with VSWR less than 2.Then the radiation pattern and beam scanning characteristics of one-dimensional E-plane and one-dimensional H-plane array are analyzed under constant amplitude in-phase excitation of the double antipodal Vivaldi antenna element.The simulation results show that in the finite array,due to the large aperture size of the antenna element itself,the sidelobe level of the pattern will be very large in the case of constant amplitude in-phase excitation at higher frequency and a large scanning angle,which limits the wide-band and wide-angle scanning ability of the array.2.The tightly coupled array elements with low VSWR characteristics are realized.Firstly,under the periodic boundary conditions,two different kinds of tightly coupled array elements are simulated,and the improved VSWR effect of loading resistance ring is analyzed.Simulation results show that the introduction of the resistance ring brings a large gain loss to the first dual polarization element,but small effect is observed in the sencond element,while the improvement of VSWR is not significant.Then,based on the analysis of the impedance characteristics of the second element,VSWR is significantly reduced by hollowing out the radiation arm of the antenna element and loading a parasitic patch directly over the center of the dipole antenna.The antenna unit get an VSWR<1.5 impendance bandwidth of 4:1 when fed ideally,and an VSWR<1.5 impendance bandwidth of 3:1 is realized when fed by bulun.The dimension of the unit fed by bulun is 0.4_h×0.4_h×0.5_h(_h corresponds to the wavelength of the highest frequency),so it is quite suitable in wide-angle scanning phased array.3.The characteristics of the array composed of the improved tightly coupled antenna elements are investigated.Firstly,the edge truncation effect of the finitely large tightly coupled array is studied.After comparing the edge short-circuit grounding and the loading of virtual elements,the truncation way of loading virtual elements is choosed for the later design of the finite array.Then,an 8×8±45°dual-polarization tightly coupled phased array antenna is proposed.The beam scanning characteristics of tightly coupled arrays and finitely large tightly coupled arrays under periodic boundary conditions are analyzed respectively.The proposed phased array antenna can achieve a wide-angle wideband performance over the broad VSWR<1.5 impendance bandwidth of 3:1,and its scanning angle in the diagonal plane(D plane)can reach±60°.Finally,the proposed array antenna is fabricated,assembled and measured.Measured results and simulated results are in good agreement.