Study On Key Technologies Of Broadband Tightly Coupled Array Antennas

With the rapid development of wireless communication technology,in order to effectively improve the transmission rate and channel capacity,and realize the multi-functional integration of communication equipment,broadband design has become the trend of integrated RF system development.As an important component of wireless communication system,antennas and arrays with broadband performance have also become a research hotspot in the field of microwave technology today.Tightly coupled array antennas have the advantages of wide band,wide angle scanning and low profile,and have become the preferred form of high performance broadband array design for each platform.This thesis is based on the tightly coupled theory to carry out the research on wide angle scanning tightly coupled array antenna,wide band directional tightly coupled array antenna and low profile omnidirectional tightly coupled array antenna,the main research contents and results are as follows.1.In view of the demand for wide angle beam tracking array antennas in electronic countermeasures,radar detection and other fields,the research on directional retrodirective wide angle scanning array based on tightly coupled theory is carried out.Firstly,based on the common mode resonance suppression technology and wide angle scanning optimization method,the design of wide angle scanning short dipole array unit covering X-band(8-12GHz)is completed by using grounded branch and periodic metal patch structure.Then,by analyzing the edge truncation effect of the finite tightly coupled array,the matching characteristics of the edge unit are improved by means of virtual element loading,and the design of the Van Atta retrodirective array is completed.Finally,through the analysis of the electromagnetic characteristics of the absorbing material,the influence of loading the absorbing material on the scattering/radiation characteristics of the antenna is studied..The designed retrodirective tightly coupled array can achieve ±60° beam coverage in X-band,the gain drop is better than 3d B in angle scanning,and the isolation between transceiver arrays is higher than 25 d B.2.The strong capacitive coupling effect is introduced into the design of broadband directional antenna based on the tightly coupled theory.Firstly,an improved open-loop dipole antenna unit design is proposed,which effectively expands the impedance bandwidth of the antenna by introducing coupling patches and parasitic dipoles.Then,a wide-band balanced balun with slotted line-microstrip line structure is used to realize the impedance transformation from 150? to 50?.Finally,based on the open-circuit truncation method and using L-shaped grounded coupling branches for the designed 4-cell linear array truncation processing,completed the design of the broadband directional tightly coupled array antenna.The operating bandwidth of the array is 1.7-6.82 GHz,and the 4-frequency coverage is achieved,the front-to-back ratio of the array is greater than 14 d B,and the average in-band gain is 9.6dBi.3.The low-profile omnidirectional tightly coupled array antenna was studied.Firstly,the coupling patch is loaded between adjacent arc dipoles to expand the low frequency operating bandwidth of the antenna.The input impedance of the arc dipole is reduced and its directionality in the sector angle domain is enhanced by introducing a parasitic dipole structure.Then,a circular array is formed by a 6-cell dipole to realize horizontally polarized omnidirectional radiation.Finally,an integrated broadband balanced balun and an equal amplitude homogeneous power divider are designed in the limited internal space of the circular array to complete the design of the low-profile omnidirectional tightly coupled array antenna.The operating bandwidth of the array is 2.06-4.03 GHz,and the gain variation in omnidirectional plane is better than 1.2d B in the whole frequency band,and the height is only 0.17 times the low frequency operating wavelength.