Adaptive airborne MTI with two-dimensional motion compensation

Clutter returns received by an airborne radar exhibit a Doppler bandwidth which depends on the platform speed, beamwidth and wavelength. Echoes of slow targets may, therefore, be buried in the clutter band and are difficult to detect. Perturbations of the flight path due to the flight dynamics of the aircraft and wind effects may cause further degradation of the MTI performance. It has been shown in earlier papers of the author that space-time FIR filters applied to the output signals of a linear array antenna can be used to compensate adaptively for the flight path component of the platform motion so that a large improvement in signal-to-clutter-plus-noise ratio (SCNR) can be obtained. Such filters are referred to as TASTE (techniques for airborne slow target extraction) methods. These ideas are extended to the compensation of transversal velocity components by means of a planar array with horizontal orientation. The influence of the system bandwidth is also investigated. The results obtained can be generalised to compensate for three-dimensional perturbations of the flight path without using an inertial navigation device