| With the rapid development of modern wireless systems,as the components for transmitting and receiving electromagnetic waves in wireless communication,the performance index of antennas plays a crucial role in the overall communication quality of wireless communication systems.In this thesis,we focus on the independent regulation of electromagnetic beam pointing,polarization and energy by transmissive electromagnetic meta-surface based multi-beam lens antenna.The main research results of the thesis can be summarized as follows.1.We demonstrate a composite meta-surface beam former to generate reconfigurable multiple orbital angular momentum(OAM)vortex waves by integrating a polarization conversion meta-mirror with a multi-functional anisotropic meta-lens.More specifically,electromagnetic fields from the feed would be firstly reflected by the meta-mirror,and then transmit through the meta-lens to form the well converged OAM vortex waves with tailored beam numbers,radiation directions and topological charges.Especially,we show that the anisotropic characteristics of the meta-lens would create different multiple OAM vortex waves when the meta-mirror is rotated or equipped with active circuits to have different polarized illuminations on the meta-lens.Our design should pave the way for the reconfigurable design of generating multiple OAM vortex waves to further expand the communication capacity.2.We demonstrate the synthesis of split dual circularly polarized(CP)beams with an additional linearly polarized(LP)radiation simultaneously from dual superposed birefringent meta-surface lenses formed of zebra crossing shaped meta-gratings.More specifically,each of the meta-surface lens is capable of generating birefringent CP refractions with different helicities and will readily achieve triple beams of different polarizations when a couple of left-hand CP(LHCP)and right-hand CP(RHCP)lobes radiating in the same direction.Polarization states of such triple-beam radiations can be specifically defined,and the vibrating electric field of each beam would thus be prescribed to form the LHCP and RHCP waves as well as a co-/cross-LP wave.Especially,we show that such a spatial aliasing of dual superposed birefringent meta-surface lenses will achieve promising aperture efficiencies for the multiple-beam generation on the basis of the complementary arrangement of different meta-gratings,and should thus pave the way for more advanced spatial-phase engineering with specific radiating characteristics using metasurfaces.3.We demonstrate a weighted gradient phase of meta-surface lenses for generating multibeams and constructing a mapping from the phase domain to the energy domain for tailored a specific pointing electromagnetic beam by calculating the phase distribution of the metasurface lenses.Meanwhile,in the asymmetric multi-beam antenna design,the principle of coherent phase cancellation is used to cancel the electromagnetic beam in the direction of sub-flap radiation.Finally,a tessellated distribution is used to cross-arrange the transmissive left-and right-circularly polarized electromagnetic meta-surface elements and the left-/ right circularly polarized beams are used to synthesize the line polarized beams since the weighted gradient phase as for controlling the multi-beams amplitude to realize four electromagnetic beams with different directions,different polarization modes and consistent energy.This way of designing multi-beam meta-surface lenses by using weighted gradient phase can realize independent control of electromagnetic beam amplitude and polarization in any direction in the space,which provides an effective way for future multi-beams radiation of lens antenna. |
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