Studies On Key Techniques Of Wide-Angle Scanning Tightly Coupled Ultrawideband Phased Array

Phased arrays are a type of antennas whose directions and shapes of the beams can be controlled flexibly by adjusting the feeding phases and amplitudes of the antenna elements.They are widely used in military and civilian fields due to their high directionality,high flexibility and large information capacity.With the rapid development of various wireless electronic technologies such as radar,communication and electronic warfare,wireless electronic systems have put forward higher requirements for phased array antennas,including low-profile and even conformal antenna arrays,ultra-wideband,wide-angle beam scanning,and so on.However,traditional broadband phased array antennas are becoming increasingly difficult to meet such challenging applicational requirements.To meet these application needs and technical challenges,a new ultra-wideband phased array technology based on the tightly coupled principle has emerged in the international antenna community in recent years.In the development process of the ultrawideband tightly coupled dipole arrays(TCDA),there are still many defects in antenna performance that need to be optimized and improved.Based on the basic principle of TCDA,this thesis focuses on the comprehensive improvement of the ultra-wideband performance,wide-angle scanning performance,low profile and lightweight performance of the TCDA.The main contents and innovative achievements of thesis are as follows:Firstly,the research background and significance of the ultra-wideband wide-angle scanning TCDA are reviewed,and the research development process of the TCDA is also briefly described.Through analyzing relevant literature,the current research status in domestic and foreign countries was summarized.Secondly,based on the basic theory of ultra-wideband antennas,the impact of metal grounds on antenna radiation performance is analyzed.Then,based on the various components of the antenna elements,three structures that affect the scanning characteristics of the ultra-wideband phased array antennas are listed.Through rigorous formula derivation,the working principle was explained,and some design ideas for achieving ultra-wideband performance were provided.Thirdly,an exploration and analysis of the key factors that affect the broadband and wide-angle scanning characteristics of TCDA are conducted.Based on the working principle of balun,the antenna feeding structure was studied theoretically,and electromagnetic simulations were conducted using an equivalent circuit model.Based on the working principle of the TCDA,several common dipole models were compared,and the stacked exponential gradient dipole antenna was selected for further research.The active VSWR of the antenna element was optimized using a dielectric matching layer,and multi-layer wide-angle matching layers were used to further optimize the impedance matching and to broaden the beam scanning range.Fourthly,the design of an ultra-wideband and wide-angle scanning phased array antenna based on the tightly coupled effect is described.Based on the analysis of the key techniques mentioned above,a single-polarized ultra-wideband and wide-angle scanning TCDA is designed.A method of changing the resonant length within the frequency band to eliminate resonant points is proposed to solve the problem of resonant points within the bandwidth of the ultra-wideband array.The designed antenna is able to scan up to 70°in E-plane and ±45° in H-plane within a frequency band range of 2-18 GHz,which is equivalent to a bandwidth of 9 times.The active VSWR of the array element is less than3.0,and the radiation efficiency is greater than 98% due to the absence of resistive materials in the design process.Finally,a 10x10 finite TCDA array was fabricated and assembled,which can be used to achieve wide-angle scanning in the E-plane.Experimental results show that the antenna array is able to scan up to 70° in E-plane and ±45° in H-plane within a bandwidth of 2-18GHz(9:1).Moreover,the profile height of the array was 0.107 times the wavelength corresponding to the lowest operating frequency.