Research On STAP Technique For Clutter And Jamming Suppression In Airborne Radar

Compared with mechanical scanning radar, airborne phased array radar has greater flexibility. Airborne radar receives strong ground clutter when it receives the target echo. Besides, it is confronted with various interferences on the modern battlefield. Ultra-low side-lobe technology can be applied to suppress side-lobe clutter, but it is difficult to suppress main-lobe clutter. Phased array radar is very difficult to achieve ultra-low side-lobe in practice; therefore, the clutter received by radar may be very strong, which degrades the target detection performance of radar greatly. Thus it's important for airborne radar to suppress clutter and interferences.Space time adaptive processing(STAP) is an important technique for airborne radar, which can suppress clutter and interferences effectively. Utilizing the characteristics of clutter and interferences, STAP adaptively forms notches in the locations of clutter and interferences in angle-Doppler domain to suppress clutter and interferences. Full dimension STAP has optimal clutter and inference suppression performance, while it fails to be implemented in practice due to large computation complexity and training samples requirement. In the increasingly complex electromagnetic environment, clutter and various interferences reduce the target detection probability and degrade the performance of parameter estimation. The amplitudes and phases of array element have errors due to poor manufacture technologies, which degrade the performance of parameter estimation and geo-location of moving targets. This thesis mainly focuses on reduced dimension STAP, anti-interference processing and error estimation of array amplitude and phase. The works of this thesis are as follows:(1) Reduced-dimension STAP. The optimal STAP and the necessity of reduced dimensional STAP for large array are discussed in the thesis. The signal model of radar echo is established, and the characteristics of the ground clutter are analyzed. Then, a novel two-stage STAP algorithm based on adaptively reduced dimension structure is proposed, where the outputs of conventional reduced dimensional STAP are used as the inputs of the cascaded STAP. Simulation results demonstrate that the cascaded STAP can suppress the main-lobe clutter as well as the side-lobe clutter.(2) Research on interference suppression. Besides of clutter, radar may also receivecontinuous carrier interference and active blanking jamming, which are induced by other electromagnetic sources. In this thesis, the signal models of the mentioned interferences are presented firstly, and related properties are analyzed. Finally, several anti-jamming methods are proposed. Simulations are implemented to demonstrate that the proposed algorithms improve the performance of moving target detection.(3) Estimation of array amplitude and phase errors. System errors, such as antenna errors, may significantly degrade STAP performance. Therefore, a method based on 1l norm is proposed to calibrate the errors of antenna gain and phase, which uses only the measured data and relative parameters of radar. Firstly, the signal model with array error is established. Secondly, a template library of clutter steering vector is built and an optimization algorithm to estimate the amplitude is presented. Finally, the amplitude and phase errors of the radar array are estimated by fitting the reconstructed data to the received data. Simulations are conducted to demonstrate the estimation performance of the proposed method.