Clutter suppression for airborne FDA-MIMO radar using multi-waveform adaptive processing and auxiliary channel STAP

Range dependent clutter suppression is a challenging problem in non-side-looking airborne radar, especially in the presence of range ambiguity. To deal with this problem, this paper proposes a two-stage adaptive clutter suppression method. It utilizes the degrees of freedom in range, angle and time domains provided by a frequency diverse array multiple-input multiple-output (FDA-MIMO) radar. In the first stage, a novel multi-waveform based adaptive beamforming in joint transmit-receive (Tx-Rx) domain is proposed for range-ambiguous clutter suppression. Analysis on second-order statistic property shows that the clutter data obtained from multiple waveforms with disjoint frequency bands are (approximately) independent and identically distributed (IID) in joint Tx-Rx spatial domain. By exploiting this characteristic, a target-free Tx-Rx covariance matrix is estimated by the IID data, which are extracted from carefully designed secondary waveforms. Therefore, a near-optimal Tx-Rx response is achieved, and range-ambiguous clutter can be suppressed effectively. In the second stage, a new auxiliary channel based space-time adaptive processing approach incorporated with range dependence compensation is devised for residual clutter suppression. It takes full advantage of the prior knowledge of clutter spectrum. Thus, excellent clutter suppression performance can be obtained by the proposed approach. Simulation results demonstrate the effectiveness of the proposed method.