Research On Wideband Two-dimensional Wide-angle Scanning Array Antennas

With the development of electronic technology,the performance requirements of all kinds of electronic equipments on antenna arrays have become more and more harsh.Wideband wide-angle scanning array antenna has attracted more and more attention.These two key features,"wideband" and "wide-angle scanning",are combined to expand the application range of array antennas.Over the past decade,researches on wideband antennas and wide-angle scanning linear arrays have been gradually mature,but we still need to find a appropriate way to design high-performance wideband two-dimensional wide-angle scanning array antenna.For two-dimensional array antennas,the feature "wide-angle scanning" has multiple meanings.On one hand,the most basic meaning of "wide-angle scanning" is wide-angle scanning in two principal plane(E plane and H plane).On the other hand,the deeper meaning of "wide-angle scanning" is two-dimensional(tapered)airspace wide-angle scanning.This paper firstly lists many research productions on wideband antennas and wide-angle scanning antennas in the past twenty or thirty years and summarizes their methods and ideas.Then the paper grasps its development trend and provides guidances and enlightenments in order to break through the limitations(such as scanning blindness)and design wideband wide-angle scanning array antennas with better performances.After analysis and summary,there are some general ideas to expand the bandwidth as follows: ideology of using smoothed physical structure(a smoothed physical structure is usually propitious to reduce the reflection coefficent and Q value and inclined to produce radiation pattern with smoothed input impedance and radiation pattern);ideology of correspondence between dipole and monopole(by ingenious design,a dipole antenna and a monopole antenna can have the same impedance under the condition of ultra-wideband,and in the meantime the impedance is deeply sensitive to the feed gap between the radiating element and the ground plane);balanced symmetrical floor structure equivalence ideology(in order to obtain broadband characteristics,the floor of a monopole antenna is generally required to have a symmetrical structure;coplanar waveguide is used as the feedline when the floor is at the same side with the patch and microstrip is used as the feedline when the floor is at the different side with the patch);grid surface equivalence ideology(in many cases,the performance ofantennas with linear and grid structures can be comparable with the performance of corresponding three-dimensional antennas,and it is easy to manufacture and consumes less material).Then,there are some methods to expand the scanning range as follows:designing an element with a wide beam(using the array active reflection coefficient controlling theory,etc.);handling and controlling array coupling(like exploring wide-angle scanning principle of tightly coupled array).After a series of analysis of array antenna theory,the active radiation pattern and the maximum scanning angle of the center elements based on microstrip patch Vivaldi antennas and all-metal Vivaldi antennas of the two dimensional array composed of the E plane and H plane are studied in this paper.Then the active VSWR of the two dimensional array,the active direction diagram of the center element and the maximum scanning angle of the array are also studied in this paper.Finally,wideband two dimensional wide-angle scanning arrays with excellent performance are obtained and improved schemes are proposed.