Moving target indicator clutter tracker

Abstract

An improved MTI (Moving Target Indicator) cancelling system that provides cancellation in the first canceller stage of clutter at a first frequency and cancellation in a second or subsequent canceller stage of clutter such as weather or chaff with a substantial doppler frequency offset from that cancelled in the first MTI canceller. The first canceller stage may be a conventional in-phase (I) and in-quadrature (Q) digital MTI unit to develop the I and Q first differences followed by a conversion of these differences into a combined first difference designated as a quantity M and representing an angle times an amplitude multiplier. This M signal is then applied to a second canceller to develop a second difference signal which is then normalized to represent a pure angle term. A computer then determines the average angular error percentage over a selected number of adjacent range bins at each range bin interval and this percent error is then multiplied by the time aligned value of M to provide an actual error and a modified value of M is developed by subtracting the actual error from the value of M. The modified first difference signal is then subtracted from the delayed first difference signal to generate a second difference output signal with the undesired clutter at different doppler frequencies being cancelled.