Research On Space Time Adaptive Processing Technology Of Wideband Airborne Phased Array Radar

Airborne early warning radar generally transmits and receives narrowband signals,which can realize target detection and target distance,angle and other parameter estimation.With the development of radar technology,it is hoped that after the target is detected,a high-resolution target distance image can be obtained to achieve target classification and recognition.In order to achieve this purpose,broadband radar needs to be used.The increase of bandwidth can improve the range resolution of the system,but at the same time signal processing becomes difficult: in the spatial domain,there is an aperture transition effect,and the envelope change of the echo signal between the array elements cannot be ignored;in the time domain,the pulses of the target and the clutter may no longer be distributed in the same distance unit within the coherent processing time(CPI),and the envelope change of the echo signal between pulses cannot be ignored.If the envelope change after the bandwidth increases is ignored and the traditional space-time adaptive method is used directly,the performance of clutter suppression and target detection will decrease significantly.Therefore,it is of great significance to develop suitable space-time processing methods for target and clutter characteristics in broadband conditions.In this thesis,the wideband airborne radar echo signal is studied,the target and clutter signal model of the wideband airborne radar is established,and the influence of the wideband signal on the space-time adaptive processing is analyzed.Aiming at the problem of target energy accumulation and clutter suppression performance degradation in traditional space-time adaptive methods,this thesis proposes two methods to solve the target energy accumulation and clutter of broadband airborne radar space-time processing from two directions of range migration correction and sub-band focusing,respectively.Suppress the problem and improve the output signal-to-noise ratio,which is more conducive to target detection.The main contents and innovations of this paper are summarized as follows:1.A wideband airborne radar signal model is established,and the space-time characteristics of clutter under wideband conditions are analyzed.Firstly,the signal model of the narrow-band airborne radar is introduced;then the signal form after the bandwidth is increased is deduced.On this basis,the target and clutter model of the wide-band airborne radar is established,and the space-time distribution of the clutter in the broadband case is analyzed.characteristic.Finally,the influence of bandwidth increase on traditional space-time adaptive processing is analyzed;2.The space-time processing method of range migration correction for wideband airborne radar is studied.Firstly,the adverse effect of range migration on target energy accumulation and the phenomenon of two-dimensional spectral broadening of clutter in broadband conditions are analyzed.Then,the process of range migration correction of echoes in pulse dimension and array element dimension by two-dimensional Keystone transform is studied.For the problem of data loss in the correction process,a method of predicting and compensating the missing data is proposed by using the autoregressive prediction model.Finally,the two-dimensional CKT-STAP method is formed by combining the processing steps of range migration correction and data compensation.Simulation experiments show that this method can improve the output signal-to-noise ratio from the two aspects of target energy accumulation efficiency and clutter suppression level,and improve the detection performance of the system;3.The space-time processing method of dimensionality reduction subband focusing in the array element domain of wideband airborne radar is studied.Firstly,the feasibility of dimensionality reduction in the array element domain in the broadband case is analyzed,and the conditions that should be satisfied by the dimensionality reduction in the sub-array domain are given.Then,the subband decomposition form of the broadband echo signal is deduced,and the space-time correlation with the subband center frequency is obtained.Then,a space-time focusing matrix construction method for broadband space-time adaptive processing is proposed,and the focusing effect of the focusing matrix on the echo signal is verified by simulation analysis.Finally,the reduced-dimensional sub-band focusing space-time adaptive The processing method,the simulation verified the effectiveness of the method.