Optimized Design Of Ultra-wideband Tightly Coupled Array Antenna

The technology of phased-array antenna is widely used in modern communication and radar system.In recent years,ultra-wideband phased array plays a more and more important role in communication and reconnaissance.As a new type of ultra wideband antenna array,tightly coupled arrays are different from the traditional methods of focusing on the unit properties,but are analyzed with the array as a whole.It uses closed unit coupling to expand the array bandwidth,which solves the problem of mutual coupling between traditional phased array units,achieving broadband and low profile.In this thesis,we mainly study the ultra wideband tightly coupled antenna array with integrated balun.First,from the Floquet theorem,the analysis method of the planar periodic array is given.Through the concept of the current layer array,the effect of the coupling effect between the units on the array bandwith is analyzed from the angle of the equivalent circuit.The corresponding relationship between the tightly coupling array model and the equivalent circuit is established which provides a theoretical basis for the design of tightly coupled arrays.A vertically placed short dipole antenna is considered as the radiation unit of the tightly coupled antenna array antenna.Based on the equivalent circuit,a coarse and thin model of tightly coupled array antenna is built.The maximum bandwidth is taken as the optimization objective,and the size of the array unit is obtained through the space mapping algorithm.The subsequent research shows that the bandwidth of the tightly coupled array can be further expanded by joint optimization of balun as a matching network and antenna unit.Finally,the short-circuit mismatch problem of tightly coupled arrays at high frequencies is analyzed.A method of loading resistive matching layer is further proposed to suppress short circuit mismatch and get wider bandwidth.Finally,the cut off effect problem of finite large tightly coupled arrays is analyzed.By extend the radiation arm of the edge element to approximate the periodic environment of the antenna,the voltage standing-wave ratio is released.Then the ultra wideband tightly coupled array is simulated,and the performance of the array is analyzed.Finally,using the space mapping optimization algorithm to optimize the feed network of the array,The 8-way power dividers are presented.