Studies On Low Scattering Techniques For Tightly Coupled Ultra-Wideband Conformal Phased Arrays

With the rapid development of modern radio technology,the application of phased array antennas are becoming more and more widespread,and the requirements for them are becoming more challenging.On the one hand,phased array antennas need to meet their basic electrical performance such as ultra-wideband and large angle beam scanning.On the other hand,in order to meet the modern militarization application,phased arrays are needed to be considered for miniaturization,low profile,low scattering,conformable,etc.In recent years,the research on tightly coupled phased arrays to achieve ultrawideband and large scan angle is more common,but the exploration of its low scattering performance is less commonly seen.Therefore,the balanced radiation and scattering performance of tightly coupled conformal ultra-wideband phased arrays is studied in depth in this thesis.The main contents or innovative points of this thesis are as follows:Firstly,the research background,significance and research development overview about the tightly coupled ultra-wideband phased array antennas are reviewed in this thesis.At the same time,the development trend of antennas’ electromagnetic scattering reduction techniques is described.Secondly,the implementation methods of traditional wideband phased array antennas and the design idea of ultra-wideband phased array based on enhanced mutual coupling effect are discussed in detail.The origin of this idea,equivalent circuit and other basic principles are also introduced.Some basic theory and implementation methods of low scattering array antennas are also reviewed.Thirdly,a tightly coupled phased array working in the operating band of 6-18 GHz is designed and simulated.The array is able to achieve a ±60° scanning in the E-plane and ±45° scanning in the H-plane,with an active VSWR less than 3.The design process and improvement measures of the model are given in detail.Fourthly,a novel method based on metamaterial absorber loading is proposed,which is able to form a 180°scattering phase difference as compared to the original array element.The loaded array element can be used to reduce the electromagnetic scattering of the tightly coupled ultra-wideband arrays,without affecting the radiation performance of the phased array.Fifthly,the above antenna array is further designed based on cylindrical carrier for conformal design,and its overall scattering and radiation performance is simulated and optimized.An olive-shaped low scattering carrier that can be used to install the tightly coupled conformal phased arrays for the low RCS measurement is also innovatively designed.Finally,the tightly coupled low scattering conformal array is fabricated and assembled.Measured radiation and scattering results are in reasonable agreement with those of the simulation results,thus verifying the feasibility of electromagnetic scattering reduction techniques of the designed tightly coupled ultra-wideband conformal phased arrays.