Range Ambiguous Clutter Rank Estimation in Airborne Element‐Pulse Coding‐Multiple‐Input Multiple‐Output Radar

ABSTRACT Space‐time adaptive processing (STAP) with element‐pulse coding (EPC)‐multiple‐input multiple‐output (MIMO) radars is capable of suppressing range ambiguous clutter in airborne radar fields. However, clutter rank has not been investigated in EPC‐MIMO radars, which is of great significance for the design of STAP algorithms, such as reduced‐rank and reduced dimension, etc. This paper studies the clutter rank estimation thoroughly. Firstly, a subspace transformation matrix including the entire clutter subspace is constructed, which is related to the spacing ratio of transmit and receive elements, the number of Doppler ambiguity and the number of range ambiguity. Secondly, the clutter rank is accurately estimated according to the subspace transformation matrix for any element spacing ratio, number of Doppler ambiguity, and number of range ambiguity. Moreover, based on the estimated clutter rank, the maximum resolvable number of range ambiguity is derived. Ultimately, the impact of channel weighting on clutter rank is analysed. Numerical results verify the accuracy of the estimated clutter rank and maximum resolvable number of range ambiguity.