Study On Electromagnetic Metasurface Based Novel Array Antennas

As one of key components of contemporary wireless communication,radar,navigation and guidance systems,antennas have higher and higher performance requirements.Artificial electromagnetic metasurfaces have been shown to be capable of manipulating propaga-tion routes and polarizations of electromagnetic waves,which have potential applications in miniaturizing antenna sizes,improving antenna gains,controlling beam directions and converting polarization states of antennas.Therefore,researches on high performance array antennas based on artificial electromagnetic metasurfaces have great theoretical significance and broad application prospects.The research works of this dissertation are supported by National Natural Science Founda-tion of China,where several artificial electromagnetic metasurface based novel array anten-nas are studied.Firstly,the research background and research significance are summarized,the research status of artificial electromagnetic metasurfaces and its applications in array an-tennas are introduced,and the relevant basic theories of the research works are discussed in this dissertation.Then,several types of novel waveguide slot array antennas and reflectarray antennas are proposed in this dissertation based on spatial angular dispersive metasurface,substrate integrated waveguide cavity metasurface and linear to circular polarization conver-sion metasurface,respectively.Finally,the summary and further study of this dissertation are also discussed.The main contributions of this dissertation can be summarized as follows.1.A tapered waveguide slot array antennas based on spatial angular dispersive metasurfaces is proposed for wide angular scanning in a narrow frequency band.Firstly,we propose a spatial angular dispersive metasurface which is shown to be capable of releasing different wavelength energies when under the illuminations of plane waves from different incident angles.And such a metasurface could function as a spatial angular filter to filter compos-ite electromagnetic waves into different monochromatic waves with different transmission angles.Then,a tapered waveguide slot array antenna is proposed and beam scanning per-formances are demonstrated when the frequency is changing,where the TE₁₀0 mode in the tapered rectangular waveguide is employed to mimic the plane wave with the gradient varied oblique incidence.Finally,two orthogonally polarized spatial angular dispersive metasur-faces are proposed and applied to the tapered waveguide to form two orthogonally polarized tapered waveguide slot array antennas,which can realize frequency scanning performances and simultaneously radiate two orthogonally polarized electromagnetic waves.Both the simulation results and experiment results demonstrate that such three tapered waveguide slot array antennas are capable of realizing wide angular scanning in a narrow frequency band.2.A substrate integrated waveguide cavity metasurface is proposed and applied to the design of waveguide slot array antennas for dual-beam radiations with dual orthogonal circular po-larizations.Firstly,a linear polarization rotator is proposed by utilizing the resonant mode of TM₁₁₀10 with rotational symmetric field distribution in substrate integrated waveguide cavities,where the strip slits etched on the back side of the cavities would couple the linearly polar-ized wave into the cavities to form the resonant mode of TM₁₁₀10 and the C-slits etched on the front side of the cavities would release such resonant mode of TM₁₁₀10 in the cavities as the lin-early polarized transmitting wave.By rotating the orientation of the C-slits,the polarization direction of the transmitting wave would also be rotated with the unchanged transmission amplitude and the transmission phase.Then,a linear to circular polarization beam splitter is proposed by introducing the gradient oriented C-slit array on the linear polarization rotator to create the opposite equivalent phase gradients for the right-hand and left-hand circularly polarized transmitting waves.Both the simulation results and experiment results show that such linear to circular polarization beam splitter could be capable of splitting a linearly po-larized electromagnetic wave into two symmetric circularly polarized waves with opposite handedness,demonstrating excellent performances of bi-anomalous refractions and polar-ization conversions simultaneously.Finally,the linear to circular polarization beam splitter is applied to the waveguide slot array antennas with two design methods,where both the de-sign methods demonstrate that such antennas could be capable of radiating two symmetric circularly polarized beams with opposite handedness.3.A linear to circular polarization conversion metasurface is proposed and applied to the design of conformal reflectarray antennas for converting the linear polarization to the cir-cular polarization with simultaneously manipulating reflecting angles.Firstly,we propose a linear to circular polarization conversion metasurface through using the 45^?-skew-rings,where characteristic mode analysis and full wave simulations show that such 45^?-skew-rings could be capable of tuning the amplitudes and phases of two orthogonally linearly polarized components of electromagnetic fields with a fixed phase difference of 90^?or-90^?,and such metasurface could function as a linear to circular polarization converter to con-vert linearly polarized waves to circularly polarized waves.Then,the convex,planar and concave meta-mirrors are designed using the linear to circular polarization converters,and such three conformal meta-mirrors demonstrate excellent performances of linear to circular polarization conversions and anomalous reflections simultaneously.Finally,the conformal meta-mirrors are extended into the designs of conformal reflectarray antennas with convex,planar and concave profiles,and such three conformal reflectarray antennas are shown to be capable of radiating highly directive circularly polarized electromagnetic waves.Both the simulation results and experiment results demonstrate that all these conformal meta-mirrors and conformal reflectarray antennas are capable of converting the linear polarization to the circular polarization with simultaneously manipulating reflecting angles.