| In recent years,the commercial and large-scale laying of 5G communication network is gradually advancing,and the 5G communication band includes microwave bands and millimeter wave bands.At present,the technology and technology related to large-scale array antennas in the microwave frequency band have been very mature,so the array antennas in the microwave band have entered the stage of large-scale deployment and application.However,the limited frequency band resources in the microwave band cannot meet the growing communication needs of people,so further research is needed on the millimeter wave band array antenna to broaden the frequency band resources.The communication of millimeter wave band array antennas has the problem of base station laying costs,signal energy loss and antenna placement space being squeezed.Holographic array antennas can enhance beam gain in a specific direction and improve the signal coverage of millimeter wave base stations,thereby reducing the number of base stations laid,efficiently utilizing laying space,while avoiding electromagnetic wave losses in other directions.In order to solve the problem of cost and loss of millimeter wave band array antennas,this paper studies two narrow beam,high gain,reconfigurable millimeter wave holographic array antennas,and designs a unit control scheme for reconfigurable holographic antennas.The specific research content is as follows:1.A rectangular waveguide millimeter wave holographic antenna was designed.The rectangular waveguide antenna is composed of a twenty-way power divider,a rectangular feeder waveguide and a horizontal gap array evenly distributed on the waveguide surface,which completes beamforming by controlling the radiation phase of the horizontal gap radiation unit.One of the 20 th equal-width power dividers is fed into the TE mode electromagnetic wave by a total feeder,which feeds the gap array on the subsequent waveguide.Based on the phase distribution of electromagnetic waves in the waveguide,according to the preset beam pointing,the waveguide gap radiation unit is controlled by switching the working state.When the array scan angle changes,the gap elements that control the distribution of different phases form a corresponding interference pattern,and when the interference pattern is excited,it will form a preset beamforming direction in free space.Through the simulation and testing of the rectangular waveguide holographic antenna model,the designed rectangular waveguide millimeter wave holographic antenna has the characteristics of narrow beam and high gain of shaped beam,which can realize large angle scanning in the two-dimensional plane.2.The control circuit of the gap switch on the waveguide is designed.The waveguide gap switch control circuit consists of a PIN tube on the gap and an FPGA control circuit for controlling the PIN tube.Among them,the gap switch control circuit is based on the on-off of the PIN diode,controlling the work of the gap unit,and the FPGA control circuit controls multiple PIN tubes to generate the interference pattern of the gap unit,thereby realizing the reconfigurable holographic antenna beamforming.The chips on both sides of the PIN diode with the gap unit are equivalent to a parallel resonant circuit,forming a short-circuit structure.The FPGA controls the short circuit of the gap unit to control the working state of the gap cell and construct the interference pattern of the radiation element on the holographic array surface.According to the preset beam pointing,when the FPGA controls the on-off of a particular PIN diode,the gap units in the working state on the array surface form a beam pointing corresponding interference pattern,which will complete the construction of the preset beam pointing.Since the short-circuit structure has the same control principle for the radiation gap in the TE mode and the TEM mode holographic array,when the electromagnetic wave transmission mode in the holographic array changes,the control circuit does not change accordingly.Through the simulation of the control circuit of the waveguide upper gap switch,it is verified that the control circuit can digitally control the interference pattern of the holographic array,and complete the beamforming of the reconfigurable holographic array.3.A substrate integrated coaxial waveguide millimeter wave holographic antenna was designed.The coaxial waveguide antenna is composed of a one-point eight-power splitter,a coaxial feeder waveguide,a periodic diaphragm structure in the waveguide and a horizontal gap array evenly distributed on the waveguide surface,and the beamforming is completed by controlling the radiation phase of the cross-gap radiation unit.One of the eight equal-amplitude noninverting power splitters is fed into the TEM mode electromagnetic wave by a total feeder,which feeds the gap array on the subsequent waveguide.Unlike rectangular waveguides,the substrate integrates a slit cell on the surface of a TEM mode electromagnetic wave excitation array transmitted through a coaxial waveguide.Compared with TE mode electromagnetic waves in rectangular waveguides,TEM mode electromagnetic waves are more conducive to achieving uniform gain distribution in the operating frequency band.The coaxial waveguide antenna uses the periodic diaphragm structure to form a high-order mode bandgap,which cuts off the transmission of TE mode electromagnetic waves in the waveguide and ensures that only TEM mode electromagnetic waves exist in the waveguide.The coaxial waveguide antenna,based on the transmission phase distribution of the TEM mode,controls the switching working state of the radiation gap unit,and realizes the narrow beam high-gain beamforming pointed at different angles.Compared to rectangular waveguides,the substrate integrated coaxial waveguide millimeter wave holographic antenna maintains high gain while having smaller gain fluctuations within the frequency band.Through the simulation of the coaxial waveguide holographic antenna model,it is verified that the designed coaxial waveguide millimeter wave holographic antenna not only has the characteristics of narrow beam and high gain shaped beam,which can achieve large-angle scanning of the two-dimensional plane,but also maintain a uniform gain distribution within the working bandwidth.In summary,by applying the principle of holographic antenna beamforming,this paper designs a millimeter wave wave holographic antenna based on TE mode rectangular waveguide to achieve a narrow beam high gain and large angle scanning of the holographic antenna in the two-dimensional plane;then the corresponding control circuit is designed for the millimeter wave holographic antenna to verify the feasibility of a reconfigurable holographic beam-shaped antenna;finally,for the gain fluctuation in the frequency band of the holographic antenna,the substrate integrated coaxial waveguide millimeter wave holographic antenna is designed,while maintaining high gain,This allows the holographic beamforming antenna to have smaller gain fluctuations within the operating frequency band. |
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