Research On Clutter Suppression For Space-Based Early Warning Radar

The space-based early warning radar(SBEWR)is intended to be utilized as critical equipment for enabling all-weather and real-time detection of faint moving targets in the airspace and nearby space in the future.Significant advantages are offered by SBEWR over existing early warning radars installed on traditional platforms,including wide coverage,great power,anti-stealth,and unrestricted deployment across borders et.al.However,as a satellite platform located at extremely high altitudes and with fast-moving speeds,the SBEWR is faced with a more complex clutter environment when dynamic target detection tasks are performed.Therefore,the development of clutter suppression methods that are more suitable for SBEWR and specifically tailored to the clutter environments encountered by SBEWR is deemed as an important task in the development process.This dissertation focuses on three aspects: the clutter model received by the SBEWR and analysis of clutter characteristics,clutter suppression method for complex clutter environment of SBEWR and diversified design of SBEWR platform.Specifically,the article conducts in-depth research on clutter suppression methods based on multi-domain signal processing to combat severe non-stationary clutter,small-sample covariance matrix estimation methods based on clutter subspace under inhomogeneous environments,and the multi-spacecraft SBEWR working model and basic signal processing methods.The detailed research contents are as follows:Chapter 2 introduces in detail the basic working model and basic parameters selection principles of SBEWR,establishes the high fidelity model and signal processing model of received ground and sea clutter.By analyzing and comparing the clutter characteristics of SBEWR with those of traditional airborne early warning radar(AEWR),the main challenges of clutter suppression for SBEWR are identified,and the future direction for developing clutter suppression algorithms is clarified.Chapter 3 investigates a method for suppressing severe range ambiguous clutter in SBEWR based on inter-pulse quadrature signals.Based on the existing common signal processing domains,the multi-domain cascade preprocessing method is used to preprocess the received complex clutter,and the received clutter with different preprocessing methods is simulated and analyzed.The proposed method can achieve better clutter suppression and moving target detection performance for severe range ambiguous clutter in SBEWR.The fourth chapter investigates a multi-domain joint dimensionality reduction adaptive clutter suppression method,specifically designed for the severe DOF extension characteristics of clutter received by SBEWR.After establishing a 3D clutter data model for the FD-PHA-MIMO SBEWR,an optimal multi-domain joint dimensionality reduction signal processing structure is determined.Finally,simulation experiments show that the proposed method can obtain good clutter suppression and moving target detection performance while reducing the operational complexity.Chapter 5 addressed the issue of estimating the clutter covariance matrix(CCM)of the cell under test(CUT)in a severely inhomogeneous clutter environment for the SBEWR.A method for estimating the CCM with a small sample size based on the clutter subspace is proposed.A training sample selection method based on the Kullback-Leibler divergence(KLD)is designed and the amplitude distribution of the training samples satisfying the conditions is spatially and temporally corrected.Finally,the reliability of the proposed method is verified by simulating inhomogeneous clutter data based on real scenarios.Chapter 6 focuses on received clutter model and clutter suppression method for multi-base space-based early warning radar.An arbitrary distributed multi-base SBEWR received clutter high fidelity model is established,and the received clutter characteristics are analyzed to show that the working model can reduce the complexity of received ground and sea clutter from the working model.In addition,an improved sparse recovery method of clutter data is proposed for the gate flap problem of centralized multi-base space-based early warning radar sparse array.Finally,the advantages of diversified development of space-based early warning radar platforms and the reliability of achieving clutter suppression and moving target detection performance are verified by means of simulation experiments.