Research On Fractal-dimension Adaptive Monopulse Algorithm For Digital Array Antenna

Monopulse technology is widely used in tracking radar because of its excellent angle measurement performance.However,it will face complex jamming in electronic warfare.Therefore,in complex jamming conditions,especially in the presence of mainlobe jamming,how to combine adaptive beamforming technology and sum-difference beam monopulse angle measurement technology organically becomes core problems and key points in the engineering application of adaptive monopulse technology.The main work of this paper is as follows:1.In the presence of mainlobe and sidelobe jamming,the split-dimensional adaptive monopulse angle measurement of uniform rectangular planar digital array antenna is studied.Firstly,a split-dimensional adaptive monopulse algorithm is designed,which decomposes the rectangular array into one-dimensional equivalent linear array of row and column dimensions.The jamming suppression and monopulse sum-difference beamforming are carried out on the one-dimensional equivalent linear array.The problem that when the sidelobe jamming share the same angle with the target in one dimension,the other dimension angle measurement performance will be deteriorated is solved.And then,an adaptive monopulse algorithm with independent split-dimensional of mainlobe and sidelobe jamming is designed.The dimension is selected independently to suppress mainlobe and sidelobe jamming.The beamforming algorithm with covariance matrix reconstruction is used to suppress mainlobe jamming in opposite dimension of monopulse angle measurement,and sidelobe jamming is suppressed in the dimension farther from the mainlobe of beam.The problem of distortion of the monopulse ratio curve near the mainlobe jamming is solved.Simulation results show that the algorithm has good monopulse angle measurement performance in the mainlobe and sidelobe jamming condition.2.The hardware and software of 2D monopulse sum-difference beam angle measurement circuit are developed.The circuit is the key module of a 2D phased array antenna monopulse angle tracking system.High performance sampling chip AD9643 and FPGA processing chip XC7K410 T are selected as the core devices to complete the hardware circuit schematic and PCB design.The FPGA software development of monopulse sum-difference beam angle measurement is completed,including ADC interface module,digital down conversion and decimation filter module,monopulse angle measurement and angle tracking module,signal detection module,upper computer interface module,etc.The high-precision measurement and tracking of target signal incidence angle is realized.3.The monopulse angle tracking system of 2D phased array antenna is tested in the microwave anechoic chamber,including channel calibration test and angle tracking test.The experimental results show that the root mean square error of monopulse angle measurement is better than 0.3 degree when the signal-to-noise ratio is 20 d B and the antenna beam width is 12 degrees.