US 4,137,533 AGranted

Angle/vector processed, phase-accumulated single vector rotation, variable order adaptive MTI processor

AssigneeUnited Technologies Corporation

InventorsGeorge T. Briechle, John A. Di Domizio, Frederik Weindling

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Abstract

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.

Claims8

Dependent claims

Adaptive moving target indicator radar signal processing apparatus for use with coherent or non-coherent radar of the type which provides return signals indicative of reflections received in each of a plurality of successive range bins as a consequence of repetitive illumination of a target area in each of a sequence of pulse repetition intervals (PRIs), comprising:

difference means responsive to said return signals for comparing the phase of signals in each range bin during each PRI with the phase of signals in a corresponding range bin of a succeeding PRI and for providing in response thereto phase signals representing estimated phase difference of clutter in succeeding PRIs of each range bin;
accumulation means responsive to said phase signals for providing summation signals indicative of the summation, modulo two pi, of the phase differences represented by said phase signals in corresponding range bins of said sequence of PRIs, said summation signals representing the estimated accumulated phase of clutter in the given range bin over said sequence of PRIs;
rotation means responsive to said return signals and to said summation signals to provide, in each range bin, rotated vector signals indicative of a vector of amplitude and angle represented by said return signals in said range bin rotated through the angle represented by said summation signals for said range bin;
and
clutter elimination means responsive to said rotation means for combining said rotated vector signals related to a like range bin in several PRIs to provide moving target signals indicative of the presence of moving targets having average doppler frequency significantly different from the estimated clutter doppler frequency related to said phase signals.

2 more elements

Adaptive moving target indicator radar signal processing apparatus for use with coherent or non-coherent radar of the type which provides I and Q signals indicative of the cosine and sine components, respectively, of the reflection vectors received in each of a plurality of successive range bins as a consequence of repetitive illumination of a target area in each of a sequence of pulse repetition intervals (PRIs), comprising:

arctangent means responsive to said I and Q signals for generating, for each range bin, angle signals indicative of the angle of the vector represented by said I and Q signals;
difference means responsive to the angle signals of each range bin within one PRI and the angle signals of a corresponding range bin of the succeeding PRI to provide a difference signal indicative of the angular difference represented by said angle signals;
vector means responsive to said difference signals for generating, for each range bin of each PRI, .DELTA.I and .DELTA.Q signals indicative of the cosine and sine components, respectively, of a unit vector having an angle represented by the corresponding one of said difference signals;
summation means responsive to said .DELTA.I and .DELTA.Q signals for providing for each given range bin of each PRI, .SIGMA..DELTA.I and .SIGMA..DELTA.Q signals as the respective summations of the .DELTA.I and .DELTA.Q signals of particular range bins close in range to and within the same PRI as said given range bin;
and
normalizing means responsive to said .SIGMA..DELTA.I and .SIGMA..DELTA.Q signals for providing for each range bin of each PRI, corresponding .DELTA.I and .DELTA.Q signals as the ratio of each of said .SIGMA..DELTA.I and .SIGMA..DELTA.Q signals, respectively, to the square root of the sum of their squares.

3 more elements

Dependencies are inferred from the claim text.