High resolution radar profiling using higher-order statistics
First Claim
1. A method of improving signal-to-noise ratio of a signal including the steps ofcomputing position independent terms of a quadruple product of return signal value samples returned from a target, said samples corresponding to each of a plurality of transmitted signals in a group of transmitted signals to form a trispectral slice which is position independent,averaging said trispectral slice with at least one other trispectral slice computed from return signals corresponding to another group of transmitted signals in accordance with said computing step,synthesizing an average group of signals which would produce the same result as said averaging step if said computing step were to be performed thereon.
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Abstract
A coherent radar is used for achieving high resolution radar imaging of a moving object in sea clutter and noise. A stored replica of the transmitted waveform is combined with the returned signal in a synchronous detector to produce in-phase and quadrature (I and Q or complex) samples. High resolution is achieved by transmitting a series of pulses, each at a different frequency, and then processing these complex samples to produce a synthetic down-range profile. To enhance the radar target or object from system noise and sea clutter, the complex I and Q (in-phase and quadrature component) samples from the radar are coherently averaged in a special two-dimensional slice of the trispectrum (e.g. quadruple product or fourth-order moment). This formulation of the fourth moment retains all important target information and suppresses Gaussian noise. Once averaged, a new set of I and Q samples are reconstructed that produce the same trispectral slice as this average. These reconstructed samples are then transformed using conventional Fourier transform methods to produce the average, or enhanced, down-range profile.
48 Citations
17 Claims
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1. A method of improving signal-to-noise ratio of a signal including the steps of
computing position independent terms of a quadruple product of return signal value samples returned from a target, said samples corresponding to each of a plurality of transmitted signals in a group of transmitted signals to form a trispectral slice which is position independent, averaging said trispectral slice with at least one other trispectral slice computed from return signals corresponding to another group of transmitted signals in accordance with said computing step, synthesizing an average group of signals which would produce the same result as said averaging step if said computing step were to be performed thereon.
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11. A system for deriving a profile of a collective target including
means for transmitting groups of signals toward a collective target, means for receiving signals returned from said collective target in response to said transmitted signals, means for converting said signals received by said means for receiving signals into in-phase and quadrature components, computing means for computing position independent terms of a quadruple product of return signal value samples returned from a target, said samples corresponding to each of a plurality of transmitted signals in a group of transmitted signals to form a trispectral slice, means for averaging said trispectral slice with at least one other trispectral slice computed from return signals corresponding to another group of transmitted signals, and means for constructing an estimate of an average group of signals which would produce the same result as said averaging means if similarly operated on by said computing means.
Specification