Design And Implementation Of Digital Array Radar Beamformer

Using the active phased array antenna and digital beamforming technique,the digital array radar(DAR)has the capabilities of simultaneous received digital multi-beam forming(DBF),multi-target detection,high-precision array calibration,continuous space-time coverage,and spatial adaptive interference suppression.By adopting Software Defined Radio(SDR)technique,the beamformer becomes more flexible and open,can realize the down-conversion of radio frequency signals and obtain baseband signals with multiple bandwidths for DBF processing.Based on a 352-element DAR project,this paper designs a high-precision iterative phase feed algorithm for wave control system and a two-stage beamformer framework for DAR.Then,the hardware circuit design,FPGA programming,and pattern testing of this beamformer are carried out.The main work of the paper includes:1.Starting from the requirements of radar functions,this section provides a digital array antenna layout plan,a detection beam design plan,and a sub-array-based receiving beam forming algorithm,which effectively reduces the complexity of DAR.Aiming at the beam pointing error caused by the digital phase shifter of wave control system,a high-precision iterative phase feeding wave control algorithm and its FPGA implementation scheme are designed.The algorithm uses the center symmetry characteristic of the array to iteratively determine the phase feeding mode of each array element,which can effectively improve the beam pointing accuracy,so that the beam pointing error is less than 0.01 degrees.In addition,the algorithm can calculate the wave-controlled phase shift in real time,with a small amount of calculation.2.On the digital array radar platform,a two-stage beamformer architecture is designed,which uses optical fiber to realize inter-stage communication.Then,the principle diagram and PCB design method of the first?stage beamformer are given,It realizes the preprocessing functions of mixing,sampling,DDC and DBF for 88 sub-array RF signals.3.This paper designs the FPGA program architecture of frequency conversion sampling and DBF preprocessing circuit,including RF front-end control module,IF sampling module,receiving DBF module,high-speed data transmission module,and wave control module.According to the radar operating waveform,the beamformer can obtain 3kinds of bandwidth baseband signals and form 9 received-beams,thereby achieving beam coverage of large airspace.4.In the darkroom environment,the performance of this beamformer is tested,including the performance test of receiving channel calibration function,wave control function,DBF function,transmitting and receiving beam patterns.The result shows that the channel phase difference is less than 1 degree after calibration,the beam width of the pattern and the null depth of the difference beam are consistent with the design value...