Design Of Waveguide Feed Array Antenna And Beam Steering

Antenna array has the advantages of high gain,strong directivity,and easy control of beam direction and shape.The requirement for beam scanning capability for array antennas promotes the continuous evolution of different beam scanning or switching techniques.The metal waveguides in the radiation and feeding systems of array antennas own the unparalleled advantages beyond other forms of transmission lines such as high power capacity and low loss,etc.Based on the different applications of beam scanning of waveguide-fed array antennas,the thesis discusses three types of beam scanning or switching systems and completes the corresponding antennas design.The following work is done.1.Design of a high gain wide-angle frequency beam scanning array based on a slotted rectangular waveguide with slow-wave line structure.The radiation slots are weighted by the Taylor synthesis,and the amplitude taper is realized to control the sidelobe level.The antenna adopts the method of bending the structure and loading the reactive structure to deal with the peak of the imaginary part of the input impedance,so as to solve the zero-crossing problem of the sudden deterioration of the VSWR at center frequency beam.Furthermore,horn and loading a phase-shifting surface are also adapted to improve the gain by reducing the phase difference on the radiation wavefront.Simulation and some measured results verify the antenna’s wide-angle frequency scanning performance and high gain characteristics include zero-crossing freqency.2.Design of multi-beam Lumberg lens antenna.The feed part of the antenna adopts the method of embeded power divider inside the waveguide feed source to obtain a compact structure and a wider beam width.The lens is constructed by using the inner and outer layers,where punch and fill method is used respectively based on the equivalent medium theory,so that the lens medium can realize nearly continuous changes in dielectric parameters.The proposed method is easy to realized and ensures broadband performance.The conformal polarization radome is designed by using double-layer periodical structure.The simulation and measurement results show that the antenna can cover 25% relative frequency bandwidth;and more than 85° coverage through 4-port switching;it can also works in two states of linear and circular polarization.3.Design of phase-frequency beam scanning waveguide slot antenna area array.The antenna realizes two-dimensional beam scanning through sub-array azimuth frequency scanning and phased pitch scanning.The frequency-scan sub-array is designed with ridge waveguide,H-plane bending,slot tapering,impedance cancellation,etc.to form a wide scanning angle,low sidelobe,and zero-crossing broadband characteristics.Subarrays are further combined to form a 32 elements array that can be used for phase-frequency 2D beam scanning.The simulation results verify the two-dimensional scanning capability of the antenna.The research content and results of the thesis can be directly used in various practical engineering applications such as radar and communication.