Medium PRF pulse doppler radar having simplified ground moving target rejection capabilities
AssigneeWestinghouse Electric Corp.
InventorsDavid H. Mooney, Jr., Keith A. Harriger
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Abstract
In a single channel medium PRF pulse doppler radar receiver, the return signal data is processed to prevent sidelobe return signals from being displayed and rejects ground moving targets up to approximately 80 knots while having no high velocity blind speeds. After the returns are filtered by a doppler filter notch for rejecting returns having a velocity substantially less than the 80 knot example, the return data undergoes three stages of correlations to reject sidelobe returns, and undergoes processing including a fourth correlation which enables the third stage of correlation to output a signal only for unambiguous ranges that contain target data in excess of the 80 knot range.
Claims9
In a single channel radar receiver responsive to return signals that include discrete sidelobe clutter returns and returns representative of targets having velocities both greater than and less than a predetermined first threshold velocity, and having means for correlating the returns to provide a first correlation signal and means for thresholding the returns over a predetermined period of time and correlating such thresholded return to provide a second correlation signal and having means including the first and second correlation signals to detect and blank the discrete sidelobe returns, and having means to correlate the blanked returns over a predetermined number of range cells to provide a third correlation signal indicative of the unambiguous range of any target return signals, the improvement of:
- a doppler notch filter operatively connected to blank return signals corresponding to target velocities below a predetermined second threshold velocity that is less than the first threshold velocity,
- means governed by the outputs of the notch filter to indicate a fast fourier transform filter number for each range gate interpulse period to generate a true velocity signal independent of pulse repetition frequency,
- means to compare the filter number during each radar look with a data value corresponding to the first threshold velocity, and
- means responsive to said comparison means and the third correlation signal to provide an output signal for each range gate indicative of the unambiguous range of only those target return signals above the first threshold velocity value.
A method of processing return signal data in a medium PRF radar receiver to distinguish target return signals corresponding to targets having a velocity in excess of a predetermined velocity from targets having a velocity less than said predetermined velocity, and sidelobe return signals, over multiple transmitted PRF's, wherein the return signal data is correlated and thresholded over a first predetermined number of unambiguous range cells for each PRF to generate respective first and second signals indicative of a second predetermined number of range cells being occupied by the return signal data and thresholded return signal data, and wherein range cell numbers are blanked in the return signal data for each PRF to remove sidelobe return signals present in the return signal data, and wherein the blanked return signal data is correlated over a third predetermined number of unambiguous range cells for each PRF to produce a third signal indicative of true target return signals present in said return data, comprising the steps of:
- filtering return signals to blank data corresponding to returns indicating a doppler shift less than a first predetermined velocity threshold,
- generating true velocity data independent of pulse repetition frequency for returns indicating a doppler shift greater than the first predetermined velocity threshold,
- comparing the true velocity data for each range with a second velocity threshold corresponding to a velocity higher than the first velocity threshold,
- generating output signal data for each true velocity data in each range cell,
- comparing the correlated true target return signals for each range cell with the true velocity data, and
- utilizing only the third correlation signals at times when the true velocity data indicates the velocity being above the second velocity threshold for a respective range.
A method of processing return signal data in a medium PRF radar receiver to distinguish main beam true target return signals representative of targets having a first predetermined threshold velocity from sidelobe return signals and true target return signals representative of targets having a second threshold velocity less than the first threshold velocity over multiple transmitted PRF's, comprising the steps of:
- filtering the return signals to blank returns having a doppler shift representative of returns with a velocity less than said second threshold velocity,
- detecting the filtered returns,
- generating data in response to the detected returns to indicate a filter number for each range gate interpulse period for generating a true velocity signal data independent of PRF,
- comparing the true velocity signal data with data corresponding to the first threshold velocity to generate an output when said data exceeds said first threshold velocity,
- unfolding the output of said comparing means over a predetermined range,
- correlating the unfolded data from said comparing means to determine a first predetermined number of occurrences of data in corresponding unambiguous range cells of said multiple PRF's,
- processing the detected filter return independent of the preceding steps to distinguish main beam true target return signals representative of targets having a velocity at least equal to the second threshold velocity from sidelobe return signals, said processing step including unfolding and correlating return signal data over a number of unambiguous range cells for each PRF to determine a second predetermined number of occurrences of data in corresponding unambiguous range cells of said multiple PRF's, and
- generating an output signal for each unambiguous range cell that includes the first and second predetermined number of occurrences.
Dependencies are inferred from the claim text.