Adaptive airborne MTI: an auxiliary channel approach

The suppression of ground clutter returns received by an airborne radar is basically a two-dimensional filtering problem, because the clutter echoes depend on two parameters (velocity, azimuth) instead of velocity only as in case of ground-based radars. This requires two-dimensional sampling (in space and time) of the backscattered echo field, which in practice is fulfilled by a coherent pulse Doppler phased array radar. Previous studies have shown that the space-time clutter covariance matrix of the order NM ¿¿ NM (N is the number of sensors, M the number of echoes) has only N + M clutter eigenvalues (instead of NM), which means that the signal vector space can be reduced. In the paper an adaptive radar receiver with AMTI (airborne MTI) capability is shown and discussed. It is shown that this AMTI receiver approximates well the theoretical optimum; however, the computational expense is drastically reduced. In view of the dramatic progress in the field of microelectronics and algorithms (e.g. systolic arrays), one can expect that such AMTI receivers will be realisable for real-time applications in the near future.