Research On Highly Integrated Wide Band Wide Scanning Angle Phased Array And Antennas With Reconfigurable Beams

During the past decade,pattern reconfigurable antennas have drawn increasing attention because they can adjust their radiation characteristics dynamically in accordance with system requirements and environmental changes,and in consequence the utilization rate of the spectrum can be greatly enhanced in the space domain.For conventional phased arrays,they may not be suitable for civilian or commercial applications due to their high costs,complexity,and low integration level.In this dissertation,highly integrated phased arrays and beam reconfigurable antennas with features of simple structure,easy fabrication and flexible control are studied.In detail,by combining substrate integrated waveguide(SIW)technology,phased array technique,and reconfigurable technology,we explore the depths of realization schemes of the beam control for different types of antennas.And on this basis,we propose several implementations of antennas with beam scanning,beam steering,beam type reconfiguration,and beamwidth reconfiguration characteristics.The main contributions of this thesis are listed below.1.Highly integrated wideband wide scanning angle phased array.A compact SIWfed aperture-coupled patch antenna(ACPA)utilizizng hybrid modes of the TE110 and TE210 resonances in the SIW cavity is first proposed,with purpose of widening the impedance bandwidth and improving the gain simultaneously.Next,an SIW-based refelction type phase shifter is designed with the features of low-cost,wide bandwidth,and continuous phase tunability,and it consists of a double-layered 90° hybrid junction and two reflective loads with annular rectangular slots dominated by varactors.Afterwards,an SIW beamforming network(BFN)is presented,including a grounded coplanar waveguide(GCPW)-to-SIW transition,a T-type two-way power divider,two Y-type two-way power dividers,and the aforementioned SIW phase shifters.Finally,a 1×4 SIW phased array is assembled in a monolithic multilayer structure,consisting of four ACPA elements and the BFN.A prototype was designed,fabricated,and measured to demonstrate that a continuous beam scanning range from-45° to 45° with the fractional bandwidth of 16.1% and a gain of up to 11 d Bi can be obtained.Accordingly the SIW technology shows superiorities in achieving monolithic wideband wide scanning angle passive phased arrays.2.Simple beam steering SIW cavity-backed slot antenna.An SIW cavity-backed triple-slot antenna fed by an off-centerd probe is proposed.First of all,the TE160 mode is excited in the rectangular cavity with the help of three parallel transverse slots placed on its broadwall,so a three-element linear array is constructed initially.Then an electrical control adjustable unit(ECAU)built with post-loaded varactors is presented.Specifically,a metal post/metallized via-hole is inserted in the SIW and then followed by annular gaps etched around it on upper and lower metal surfaces,whereat varactors are placed across the gaps.To persturb the E-field in the SIW cavity,a pair of the ECAUs are embeded between the adjacent slots.The excitation amplitude and phase of the array can be electrically controlled,therefore the main beam direction can be switched to different elevation angles.At last,additional ECAUs are inserted at opposite ends of the two side slots for sidelobe reduction.The measured results show that the antenna is capable of steering the main beam from-30°to 41° with a maximum gain of 9.2d Bi.The compact and simple structure,ease of fabrication,and well-controlled radiation patterns of the proposed design are experimentally verified.3.Multi-polarization antenna with reconfigurable broadside and conical beams.A method of realizing pattern diversity patch antenna with three polarization directions is first presented.By concentrically placing a thin cylindrical dielectric with high permittivity underneath a ring patch,we can lower the resonant frequency of TM02 mode,whereas the resonant frequency of TM11 modes remains unchanged.So the anntenna is able to provide a vertical polarization with an omnidirectional radiation pattern and two orthogonal horizontal polarizations with unidirectional patterns at the same frequency.Afterwards,a new type of quadri-strip-fed dielectric resonator antenna(DRA)is proposed.The core idea of this design is based on resonant frequencies of the unidirectional HEM11? mode and the omnidirectional TM01? mode of a cylindrical DRA can overlap by tactfully removing a concentric annular column from its interior.In other words,part of the original high permittivity dielectric is substituted for air dielectric in the strongest E-field area for the HEM11? resonance,thereby greatly increasing the associated resonant frequency.Furthermore,a center-loaded metal post helps to improve the impedance matching of the TM01? resonance significantly.Then a switchable feed network is designed to implement diverse phase distributions of four output ports.It eventually provides quad-port in-phase excitation,dual-port differential excitations,and quad-port sequentially rotated phase excitations for a vertical linear polarization(LP),±45° slant horizontal LPs,and two circular polarizations(CPs),respectively.The measured results show that the overlapping impedance bandwidth of 36.7% for all the states and axialratio bandwidth of 32.1% for the CPs are obtained.4.Wideband beamwidth reconfigurable magneto-electric dipole antenna.A beamwidth reconfigurable linear array antenna utilizing three magneto-electric(ME)dipole antenna elements with no need for a complex feeding network is presented.In this design,the ME dipole antenna elements are differentially excited by three parallel transverse resonant slots etched on the broad wall of a substrate integrated waveguide(SIW)cavity.By symmetrically embedding four copper posts that are connected to varactor diodes between the adjacent slots,the electric field perturbation in the SIW cavity can be realized by manipulation of the varactors.In other words,altering bias voltage of all the varactors simultaneously could offer granular control over the excitation amplitude and phase of the antenna elements.Consequently,continuously variable beamwidth of the antenna can be obtained under electronic control.A fully operational prototype was designed,fabricated,and tested to validate the proposed design.Measured results indicate that the overlapped-10 d B impedance bandwidth of the proposed antenna is 19.6% and the half-power beamwidth is capable of dynamtical adjusting from 39° to 107° within the broad operation band.