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US 7,248,343 B2Granted
Amplitude-weighted spatial coherent processing for LADAR system
AssigneeRaytheon Company
InventorsSilvio Antonio Cardero, Robert Edmund Majewski
Life of this patent
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Abstract
A laser radar (LADAR) system is provided with amplitude-weighted spatial coherent processing. An amplitude-weighted sum of time domain signals arising from several detectors within a detector array is formed and used for range doppler processing. Weighting coefficients are chosen to be proportional to the signal amplitude present for each of the separate signals from each detector within the array. The amplitude coefficients are determined using target returned energy arising from a continuous wave (CW) porch portion of the transmitted waveform. Amplitude-weighted spatial coherent processing improves the carrier-to-noise ratio (CNR).
Claims21
A laser radar (LADAR) system for sensing a target, comprising:
- a laser for illuminating the target with a target signal waveform;
- a heterodyne detector array comprising an M×N array of detectors for detecting the target signal waveform reflected back from the target, each of the detectors producing a respective time domain signal for use in range doppler processing to sense the target;
- amplitude weighting processing circuitry that calculates a set of amplitude weighting coefficients, the amplitude weighting coefficients being proportional to the time domain signal amplitude for each of the detectors, wherein the amplitude weighting processing circuitry comprises:
- circuitry that calculates the amplitude of an imaging portion of the respective time domain signals;
- and
- a host processor which calculates amplitude-weighted coefficients based on the calculated amplitudes of the imaging portion of each of the respective time domain signals;
- and
- range doppler processing circuitry for forming a summation of the respective time domain signals using the amplitude weighting coefficients, and processing the summation to develop an output representing the target;
- wherein the circuitry that calculates the amplitude of the imaging portion of the respective time domain signals comprises:
- an analog-to-digital (A/D) converter which converts the time domain signal into a digital signal;
- an accumulator which sums the square of the imaging portion of each time domain signal;
- and
- a divider circuit which divides the square-root of the square of the imaging portion of each time domain signal by a constant false alarm rate (CFAR) threshold.
10 more elements
A laser radar (LADAR) system for sensing a target, comprising:
- a laser for illuminating the target with a target signal waveform;
- a heterodyne detector array comprising an M×N array of detectors for detecting the target signal waveform reflected back from the target, each of the detectors producing a respective time domain signal for use in range doppler processing to sense the target;
- amplitude weighting processing circuitry for calculating a set of amplitude weighting coefficients, the amplitude weighting coefficients being proportional to the time domain signal amplitude for each of the detectors;
- and
- range doppler processing circuitry for forming a summation of the respective time domain signals using the amplitude weighting coefficients, and processing the summation to develop an output representing the target,
- wherein the target signal waveform includes a porch portion followed by an imaging portion, and the amplitude weighting processing circuitry comprises:
- circuitry for calculating the amplitude of the porch portion of the respective time domain signals;
- and
- a host processor which calculates amplitude-weighted coefficients based on the calculated amplitudes of the porch portion of each of the respective time domain signals.
6 more elements
A laser radar (LADAR) method for sensing a target, the method comprising:
- illuminating the target with a target signal waveform;
- detecting the target signal waveform reflected back from the target using a heterodyne detector array, each of the detectors producing a respective time domain signal;
- calculating a plurality of amplitude weighting coefficients, the amplitude weighting coefficients being proportional to the time domain signal amplitude for each of the detectors, wherein calculating a plurality of amplitude weighting coefficients includes selectively receiving an imaging portion of the respective time domain signals and calculating the amplitude of the imaging portion of the respective time domain signals;
- weighting the respective time domain signals using the amplitude weighting coefficients;
- and
- summing the amplitude-weighted time domain signals and processing the summation to develop an output representing the target;
- wherein calculating the amplitude of the imaging portion of the respective time domain signals includes:
- analog-to-digital (A/D) converting at least a portion of the time domain signals into digital signals;
- applying an accumulator to the A/D converted signals to integrate the A/D converted signal amplitude squared;
- and
- dividing the square-root of the A/D converted signal amplitude squared by a constant false alarm rate threshold (CFAR).
8 more elements
A laser radar (LADAR) method for sensing a target, the method comprising:
- illuminating the target with a target signal waveform;
- detecting the target signal waveform reflected back from the target using a heterodyne detector array, each of the detectors producing a respective time domain signal;
- calculating a plurality of amplitude weighting coefficients, the amplitude weighting coefficients being proportional to the time domain signal amplitude for each of the detectors;
- weighting the respective time domain signals using the amplitude weighting coefficients;
- and
- summing the amplitude-weighted time domain signals and processing the summation to develop an output representing the target,
- wherein calculating a plurality of amplitude weighting coefficients includes:
- selectively receiving the porch portion of the respective time domain signals;
- and
- calculating the amplitude of the porch portion of the respective time domain signals.
7 more elements
Dependencies are inferred from the claim text.