Studies On The Thinned Array Techniques For Ultra-wideband Phased Antenna Arrays

In various modern wireless radio systems,the increasing technical challenges such as the high gain,wideband,and wide spatial coverage for phased array antennas are driving the development of phased array antennas towards large-scale,ultra-wideband,and wide-angle scanning.At the same time,more attention has been focused on complicated hardware system,difficult heat dissipation,and low cost.The application of thinned arrays can be used to solve the above problems well.Although the thinned array synthesis techniques based on the stochastic optimization algorithm are widely used,they are still facing many challenges,such as easy to fall into local optimum,heavy calculations and so on.Focused on the aforementioned background,this thesis proposed an optimization algorithm suitable for the thinned array synthesis of ultra-wideband phased arrays,and realized the design of a tightly coupled thinned array with ultrawideband scanning characteristic in C-Ku band.The contents of this thesis are as follows:Firstly,the research background and significance of thinned array technology of ultra-wideband phased arrays are briefly introduced,and the research history and existing problems of array antenna synthesis at home and abroad are reviewed.Moreover,the research status of tightly coupled ultra-wideband phased array is briefly summarized.Secondly,a multi-agent genetic algorithm was applied to array synthesis for the first time,and two improved strategies are innovatively introduced to improve the search ability and speed up the convergence speed of the algorithm.The improved multi-agent genetic algorithm is applied to several array synthesis examples,such as difference pattern synthesis and thinned array synthesis.Numerical results show that the proposed algorithm outperforms other traditional algorithms.The wide-angle scanning characteristics of large-scale thinned phased arrays are also discussed.Thirdly,a tightly coupled array element of octagonal rings and interdigital capacitive coupling is designed,where split resonant rings are loaded as the WAIM layer.This element uses the unbalanced feed structure,four symmetrical pairs of shorting posts,and punched dielectric substrates for balancing the high and low resonance frequency.Numerical results show that the tightly coupled element is able to achieve the wide-angle scanning performance within a 3:1 bandwidth in an infinite periodic environment.Fourthly,a 7×14 octagonal ring tightly coupled array with split resonant ring is fabricated and measured.The voltage standing wave ratio(VSWR)characteristics and far-field array pattern are measured.The antenna radiation characteristics of the ultrawideband tightly coupled thinned array are then obtained by the active element pattern synthesis approach.Finally,a multi-objective optimization algorithm based on multi-agent genetic algorithm is proposed.Based on the proposed algorithm,the multi-objective collaborative optimization of the radiation/scattering performance including the sidelobe levels,directivity,and scattering levels of the thinned array antenna are discussed,and some useful guiding conclusions are obtained.