United Technologies Corporation

John A Di Domizio

George T Briechle

Frederik Weindling

Douglas Ell

In-phase (I) and quadrature (Q) radar return signals are converted to phase to provide phase difference between like range bins of successive pulse repetition intervals (PRI's), the phase differences being reconverted to I and Q format for accumulation across multi-range-bin windows surrounding each range bin to be processed, the normalized range bin accumulations being continuously accumulated in the angle domain, in successive PRI's, to provide clutter phase angle estimates used to rotate incoming target video vectors, a single time, back to the estimated zero-doppler phase of the first PRI of a multi-PRI batch for clutter-elimination filtering. Third-order and fourth-order filtering (utilizing four-PRI and five-PRI batches, respectively), is achieved on a constant one-out-of-four PRI output basis by utilizing the same weighted data for the highest PRI of one fourth-order batch and the lowest PRI of the next higher fourth-order batch, which is rendered possible by the continuous accumulation of estimated phases, over successive PRI's.

Angle/vector processed, phase-accumulated single vector rotation,

In an AMTI radar of the type in which the difference between the phase of a current radar return signal and the phase of a radar return signal in a corresponding range bin of a preceding pulse repetition interval (PRI) is averaged over a number of range bins in the range vicinity of the current range bin, phase differences for current range bins are determined as being clutter-like or non-clutter-like by comparison with the previously-determined average phase difference by means of a rectangular distance discriminator which compares the normalized in-phase and quadrature components (cosine and sine, respectively) of the current phase difference with the normalized in-phase and quadrature components of the average phase difference in a rectangular distance discriminator. The rectangular distance discriminator sums the absolute values of the in-phase difference and the quadrature difference and compares them against a rectangular distance discriminant, which in a preferred embodiment is unity. When the summation of the absolute value of the in-phase and quadrature differences exceed the discriminant, the previously-determined phase average components are reintroduced into the phase averaging process; but when it is less than the discriminant, the current phase differences are introduced into the phase averaging process.

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Norwalk, CT, United States of America

John A Di Domizio