Local degrees of freedom of clutter for airborne space-time adaptive processing radar with subarrays

Space-time adaptive processing (STAP) is an advanced technique for airborne radar to mitigate clutter and detect moving targets effectively. Based on adaptive radar theory, the degrees-of-freedom of a STAP processor should be larger than that of a clutter. In this study, the local degrees-of-freedom (LDOF) of clutter for reduced-dimensional STAP (RD-STAP) methods with subarray configurations are studied. The LDOF formulas are proposed and verified by simulations. With these formulas, the LDOFs of clutter will collapse under certain radar configurations, which are favourable for clutter mitigation. Therefore these formulas could be used as guidance for STAP radar to choose appropriate system parameters and processing methods.