| The all-digital beamforming technology means that each antenna element in the antenna array can individually control the amplitude and phase of its waveform through digital means to achieve efficient and precise steering control of the spatial beam.Its changeable and flexible working characteristics are gradually being used in today’s advanced radar and communications fields.With the advancement of large-scale digital integrated circuit technology,digital array multi-beam forming systems under airborne conditions have more room for development in miniaturization and integration.Based on the "Digital Multi-Beam Antenna Integrated Processing Extension" project,this paper has completed the development of a small all-digital beamforming processor.The main tasks of this paper are as follows:Analyzed the shortcomings of the existing digital array beamforming system’s transmission system,and took miniaturization,integration,and digitization as the main ideas,and proposed a high and intermediate frequency transceiver scheme based on radio frequency transceivers,completing the light and small all-digital array beamforming The hardware design of the processor includes four 16-channel high and intermediate frequency signal transceiver boards,a DBF processing main control board,and a signal interconnect VPX backplane.At the same time,an in-depth analysis of the hardware design difficulties of the high and intermediate frequency transceiver circuit,power supply circuit and synchronous clock circuit is carried out,and specific solutions are proposed,which break through the difficulty of multi-channel hardware synchronization of the transceiver all-digital array.The working mechanism of the software-based all-digital array platform is studied.According to the configurable requirements of the Virtex-7 series FPGA on the channel parameters of the RF transceiver AD9371,the smallest system module based on the embedded processor soft core Microblaze is built,and the C language is completed.The bottom-level driver development platform design of the compilation environment realizes the software initialization process and parameter configuration of AD9371.Aiming at the random initial phase error and multi-channel fixed amplitude-phase error of multiple AD9371 IF local oscillators,the respective error sources are analyzed,and the mathematical model of multi-channel amplitude-phase error calibration is established,and an "automatic online calibration" is proposed.The software calibration method combined with "power division error compensation" completes the system’s transceiver multi-channel amplitude and phase error calibration test.The Digital Beam Forming(DBF)algorithms of the all-digital transceiver array are studied,including static DBF,low sidelobe DBF,and interference trap zero DBF based on the linear constraint minimum variance LCMV criterion.Matlab software is used to map each algorithm.Modeling and simulation,completed the design of the DBF weight vector calculation module through the High Level Synthesis(HLS)tool,realized the two-stage digital beamforming in the FPGA platform,and finally demonstrated the emission direction of the system in the darkroom environment Figure experimental results. |
