Research On Ultra-wide Bandwidth Angle Scanning Tightly Coupled Array Antenn

With the continuous improvement of communication rate and communication capacity,the ultra-wideband phased array antenna has attracted extensive attention for its high-speed electrical scanning performance of wideband,wide-angle scanning.Different from the traditional ultra-wideband phased array,the tightly coupled array antenna overcomes the limitations of element size and spacing in the ultra-wideband array by using the strong coupling between elements,and can obtain multiple octave bandwidth and wide-angle scanning performance,which has become a hot spot in recent years.This thesis studies two kinds of tightly coupled phased array antennas — multi-layer planar printed tightly coupled dipole array and tightly coupled Vivaldi array antennas.The two types of ultra-broadband wide-angle scanning tightly coupled array antennas are developed to explore their bandwidth and crosspolarization performance.Firstly,we research the multi-layer planar printed dual-polarized tightly coupled dipole arrays with unbalanced feeds.Coupling disk is etched and registered beneath the dipoles and connected with a via to the ground plane,which can remove the common-mode resonance and can augment interdipole capacitance simultaneously.In addition,multiple horizontal metal strips are connected to the dipole feed line vias,forming a “rib” structure,to increase the capacitive coupling and affect impedance matching.The bandwidth was successfully extended to 3.93-17.76GHz(Active VSWR<3).For the demand of radio frequency multi-layer printing,the substrate and processing technology were extensively investigated,and a 11×10-array was successfully developed.Besides,the effects of element mutual coupling and different array sizes on the performance of finite array are studied based on this array’s experimental test.The study shows that: for multi-layer planar printed tightly coupled dipole arrays,to verify the design performance of the VSWR of the element in large array,the mutual coupling larger than-25 dB must be fully taken into account.The test results of the 7×7-array are in good agreement with the simulated ones in this thesis.Secondly,the tightly coupled Vivaldi array antenna with excellent bandwidth performance is studied.The problems such as large cross polarization caused by high profile longitudinal current and standing wave singularities in wide-angle scanning of Vivaldi end-fire array were deeply analyzed.The technology of radiating fin slices was adopted to suppress longitudinal current and reduce cross-polarization,and metallic vias were loaded along the edge of doublesided slot line to remove standing wave singularities.The ultra-wideband low cross-polarized sliced Vivaldi antenna array unit is designed to achieve a bandwidth of 9:1(2-18 GHz,Active VSWR<2)when scanning in broadside.The simulation studied the mutual coupling of the finite array elements and the characteristics of the pattern,analyzed the influence of the truncation effect.Finally,the 9×9 finite Vivaldi array antenna was developed,which made the test results consistent with the finite array simulation results and verified the correctness of the design.The multi-layer planar printed dual-polarized tightly coupled dipole array developed in this thesis has low profile,bandwidth and wide-angle scanning performance,and the tightly coupled Vivaldi array antenna has a bandwidth of 9:1.The realization of ultra-wideband and wide-angle scanning array antennas will greatly reduce the weight and space occupied by the antenna in multi-functional systems,and even reduce the cost,volume and improve the versatility of the whole system,which will have important application prospects in military or civil communication systems.