Research On Angle Measurement Technologies For Elliptical Array Radar

Airborne early warning aircraft is responsible for the tasks of airborne warning and control/guide.It need to measure the three-dimensional coordinates of the targets and among which the low-flying fighters are an important target.Due to the limitation of the aerodynamic characteristics of the aircraft,the vertical aperture of the airborne radar antenna is unlikely to be very large,which will lead to a wider elevation beamwidth.Usually,the height measurement precision is difficult to meet the combat requirements,and the currently equipped airborne early warning radar can't be called three-coordinate radar in the true sense.Therefore,it is be of great application value to research in how to improve the angle measurement accuracy for elevation angle in the application of actual airborne early warning radar equipment.Firstly,the traditional monopulse angle measurement under the elliptical array radar is achieved.The characteristics of the normalized monopulse error curved surface is analysed and the two-dimension monopulse ratio grid for azimuth and elevation direction is also established.The angle measurement result for traditional monopulse is finally obtained by looking up this two-dimension table and utilizing the interpolation method.Secondly,the four-channel monopulse angle measurement method for elliptical array radar is proposed.Previous researches about four-channel monopulse in rectangular array is extended into the application of elliptical array,and the significance of the delta-delta signal to angle measurement is alalysed in this thesis.The four-channel monopulse angle estimation method is obtained by fusing the two angle estimates under two sets of monopulse ratios.Simulation results show that the angle measurement accuracy of four-channel monopulse is higher than that of the traditional monopulse,especially when the target deviates from the beam pointing direction.Finally,the maximum likelihood angle estimation method for elliptical array radar is proposed.In order to achieve the estimation of elevation angle,the elliptical array is divided into row sub-arrays.The sub-array level received signal is established and the maximum likelihood angle estimation algorithm is derived based on this.Simulation results show that the angle measurement accuracy of the maximum likelihood angle estimation method is higher than that of the traditional monopulse,and the angle estimation performance will not change when the target location varies.