Beam Scanning Antennas Based On Dispersion Characteristics Of Waveguides

This dissertation presents lens designs based on dispersion characteristics of metallic parallel-plate waveguide(MPPW).At millimeter frequencies,partially dielectric-filled and corrugated MPPWs are utilized to design modified Luneburg and planar lens antennas for one-dimensional(ID)beam scanning.Furthermore,by vertically stacking multiple modified Luneburg lens antennas together,a lens antenna array can be realized to achieve two-dimensional(2D)beam scanning at horizontal and vertical planes,respectively.In addition,the beam scanning based on the electronic tunability of graphene is studied.The main topics of this thesis are as follows:1.An 1D beam scanning modified Luneburg lens antenna is proposed.Through switching the excitation of the horizontal feed array,wide-angle 1D beam scanning at horizontal plane is realized.This approach avoids the half wavelength limitation for the horizontal array,which benefits a lot for the integration of feed array and T/R components,reduces the complexity and fabrication difficulty significantly,and improves the reliability.2.A 2D beam scanning modified Luneburg lens antenna array is proposed.By switching the excitations of the horizontal feeders and tuning the amplitudes and the phases of the vertical lens antennas,wide-angle 2D beam scannings at horizontal and vertical planes are realized.This approach requires switches and phase shifters for horizontal and vertical beam scanning,which reduces the number of phase shifters and the time for system calibration,compared to traditional phased arrays.Furthermore,a module design is given for the integrated beam switching network.The horizontal feeding array is divided into multiple modules,which can be individually controlled by the digital circuits.Thus,digitally controllable beam scanning at horizontal plane can be realized.This approach improves the stability of the system and reduces the mutual couplings between feeding modules,which benefits the integration and maintenance of the system.3.Lens antennas based on corrugated MPPW are presented.The dispersion characteristics of the corrugated waveguide can be controlled by adjusting the parameters of the corrugations.Thus,the effective index of refraction of the corrugated waveguide can be designed to realize the required phase delay to transform cylindrical waves into plane waves.A linear array of waveguide slot antennas is used to feed the corrugation lens for multiple beam scanning.The all-metal lens antenna does not require dielectrics,which makes it easy and low-cost to fabricate and can work under tough environments.4.A multi-stage waveguide array based on graphene is proposed,which utilizes the electronic tunability of graphene to control the phases of the propagating surface waves to realize 1D electronic beam scanning at mid-infrared frequencies.The waveguide array consists of multiple waveguides with different effective indexes of refraction side by side,which leads to a fixed progressive phase difference determining the direction of the outcoming beam.Trough cascading multiple waveguide arrays with different progressive phase differences and switching the on/off statuses of the gate voltage between the graphene and the doped silicon substrate,the accumulated phase delays of the surface waves along the path can be changed.Thus,different final progressive phase differences can be achieved,and the beam scanning can be controlled electronically.