Research On Antenna Array Technology Based On Tightly Coupled Structure

Along with the increasing demand of modern communication technology for information transmission rate and channel capacity,wideband array antenna has been widely used in modern communication technology instead of traditional single antenna unit.In military applications,phased array radar is usually composed of broadband array antenna.However,conventional wideband array antenna is limited by the coupling effect between the units and cannot achieve wider working bandwidth.Tightly coupled array antenna breaks the shackles of traditional design,and utilizes the mutual coupling effect between adjacent units to expand the bandwidth of the antenna skillfully.In this thesis,the performance of array antenna is discussed based on tightly coupled structure.The work of this thesis is mainly divided into the following parts: 1.Firstly,the research background and research status of broadband array antenna and tightly coupled phased array antenna are introduced respectively.Secondly,the basic electrical parameters involved in the design of tightly coupled array antennas are described,the basic working principle of array antenna and the pattern multiplication are analyzed,and the scanning principle of one-dimensional linear array and two-dimensional planar array antenna is given,respectively.Thirdly,the basic theory of dipole antenna which is the array element designed in this thesis is introduced.Finally,the realization principle of ultra wideband of tightly coupled array antenna is analyzed in detail in the view of equivalent circuit.2.On the basis of array antenna theory,a tightly coupled array antenna based on band-pass frequency selective surface with a bandwidth of 1 GHz-10 GHz is designed.Among the currently known literature,the bandwidth-broadening method for a tightly-coupled array antenna is to load a resistive frequency selective surface between the antenna and the metal reflector,and the bandwidth of the antenna is extended by absorbing the backward radiation wave which causes the short-circuit point.In this thesis,a frequency selective surface with band-pass characteristics at short circuit points is designed to replace the resistive frequency selective surface and metal reflector,which simplifies the antenna structure while expanding the bandwidth of the antenna.Then,the 8×8 elements tightly coupled antenna array is simulated and analyzed,the feasibility of the scheme is verified through physical processing and testing.3.Based on the theory of electromagnetic metamaterials,a metasurface-based tightly-coupled array antenna unit and a low radar cross section(RCS)tightly-coupled array antenna based on artificial magnetic conductors are designed respectively.A dielectric matching layer is usually used to adjust the antenna's matching in designing a tightly coupled array antenna.This thesis designs a metasurface instead of the dielectric matching layer,which not only improves the antenna matching performance,but also reduces the weight of the antenna and facilitates installation.Based on the principle of RCS reduction by using artificial magnetic conductors,two tightly coupled array antenna units with different reflection phase differences of 180°±37° degree are designed respectively by loading a periodic metal patch above the dipole.The radiation performance of the unit shows that the loading of the periodic metal patch improves the matching of the antenna elements and slightly increases the gain of the antenna unit.The two modules are arranged in a chessboard structure to form 8×8 array antennas,and their scattering properties are analyzed.Compared with the tightly coupled array antennas of the same size without the periodic metal patch,the result shows that the RCS of the tightly-coupled array antenna based on artificial magnetic conductor can be reduced to varying degrees when the antenna is irradiated by the electromagnetic wave with different polarization.