Research On Wide-angle Scanning Array Antenna Based On Metamaterials

Transformation optics(TO),also known as transformation electromagnetics,is a theoretical method which can control electromagnetic waves according to people's wishes in recent years.The theory is appropriate for any electromagnetic phenomena.The core theory of TO is the coordinate transformation in space,that is to say,constructing the mapping relationship between different coordinate systems,meanwhile,the constitutive parameters of the medium in the transformation space will change,and some metamaterial arise.These metamaterial will generate special electromagnetic properties due to strong resonance which causes narrow bandwidth and high loss inevitably.In order to solve these problems,the theory of QCTO appear.This theory preserves the isotropy,low loss and wide bandwidth of the transformation space,and make it possibly to construct transformation space by pure dielectric material.In this paper,the theory of the QCTO is applied to the design of the array antenna.The main contents are as follows.1? Based on the form invariance of the Maxwell equations before and after the transformation,the virtual space and physical space are designed by applying the theory of QCTO.Under the same excitation conditions,the far-field radiation field of the conformal array antenna in the physical space is equivalent to that of the linear array antenna in the virtual space.2? In two-dimensional case,the distribution of electromagnetic constitutive parameters in physical space is calculated and then discretized.A frame-shaped dielectric unit whose electric size is much smaller than the wavelength is designed,by controlling its structural parameters and filling other dielectric material in the frame hole,the effective permittivity of the whole unit can be changed in a certain range.3? In the X band,a dielectric lens is fabricated to cover on a conformal array made up of microstrip antenna which arranged on the surface of symmetrical cylinder.The simulation results show that the conformal array with lens are excited by the simple linear phase distribution of linear array can realize the same radiation characteristics as linear array at a wide-angle scanning range from-60° to+60° on the H-plane.Comparing with the linear array,the conformal array with lens has a higher directivity.4? An asymmetric dielectric lens is fabricated by 3D printing technology to cover on a conformal array antenna at the central frequency of 8GHz.The conformal surface is also asymmetrical and has larger curvature.Based on the Wilkinson power divider,the phase-shift network is designed to feed different microstrip antenna units.The whole lens antenna system is simulated and manufactured.The results show that the radiation characteristics of conformal array antenna with asymmetrical lens designed by the QCTO can also be equivalent to that of linear array in the free space,which verifies that the TO can control the electromagnetic wave.The research in this paper shows that the dielectric lens designed by the QCTO can control the propagation of electromagnetic waves.In addition,the linear array is equivalent to conformal array with the presence of a specially designed space,at the same time,the complex optimization process of conformal array design is omitted,which provides a new idea for the design of conformal array antenna and other antenna research fields.