HF interference mitigation using STAP with dynamic degrees of freedom allocation

A variation of space-time adaptive processing (STAP) allowing dynamic allocation of spatial and range (fast time) degrees of freedom on a beam-by-beam basis is introduced. This technique tailors the adaptive processing to the prevailing interference characteristics within each beam, making use of both spatial and range adaptive processing. An added benefit is that the algorithm also takes finite sample support issues into account when regulating the number of degrees of freedom used. The allocation of degrees of freedom is made using metrics which measure the expected adaptive processing gains obtained using purely space and range processing. The technique is applied to a passive data-set collected using Jindalee Facility Alice Springs skywave over-the-horizon (OTH) radar located in central Australia, yielding a mean noise level for all beams only 0.6 dB higher than that obtained using the (unknown) optimal degrees of freedom allocation.