Synthetic aperture radar guidance system and method of operating same
First Claim
1. A synthetic aperture radar system comprising:
- a) means, responsive to a controller, for transmitting a plurality of radio frequency pulses, each pulse having a frequency range wherein the frequency of each pulse changes at a linear rate during the pulse wherein an initial frequency of each successive pulse is outside the frequency range of an immediate preceding pulse; and
b) means, responsive to the controller, for adjusting the transmission time of a successive pulse to receive a reflection of a prior pulse at an interval between the transmission of two successive pulses.
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Accused Products
Abstract
A synthetic aperture radar guidance system adapted for use in a guided missile is described wherein the frequency of the transmitted pulses changes with time with a chirp slope which varies with range. The time between pulses also changes as a function of range. The desired values of the chirp slope and the interpulse interval are computed for all values within a range of interest and stored. Furthermore, the operating parameters of the SAR are changed as the range changes. The time intervals and frequencies are selected to avoid interruption ambiguities and eclipsing. The phase and frequency of the synthesized signal are controlled to adjust for motion of a vehicle on which the SAR is mounted. The SAR is operated in several modes. In a search mode, the beam of transmitted pulses is steered across a mapping area to form a plurality of patches of the mapping area. The patches are combined into one map of the entire area. Each pixel of the map is compared with a target template until a match is provided. Then the SAR operates in track mode wherein a correlation process ensures the missile is steered toward the target area using a template provided using known feature data.
110 Citations
17 Claims
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1. A synthetic aperture radar system comprising:
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a) means, responsive to a controller, for transmitting a plurality of radio frequency pulses, each pulse having a frequency range wherein the frequency of each pulse changes at a linear rate during the pulse wherein an initial frequency of each successive pulse is outside the frequency range of an immediate preceding pulse; and b) means, responsive to the controller, for adjusting the transmission time of a successive pulse to receive a reflection of a prior pulse at an interval between the transmission of two successive pulses. - View Dependent Claims (2, 3, 4, 5)
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6. A method of operating a synthetic aperture radar comprising the steps of:
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a) transmitting a series of chirped pulses; b) receiving reflections of transmitted pulses from an object at a range from the synthetic aperture radar and mixing the received signal with a chirped pulse to produce a dechirped signal; and c) mixing the dechirped signal with a controllable signal and changing the frequency and phase of the controllable signal as the range changes. - View Dependent Claims (7, 8, 9)
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10. A method of operating a synthetic aperture radar on a flying object to form a map of an area on the ground encompassing a plurality of pixels, each representing a location on the ground, the method comprising the steps of:
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a) pointing a beam of radio frequency energy at a location on the ground; b) receiving reflections from objects within the patch of ground centered at the locations during a dwell time; c) forming an array of pixels from the received signal, the values of each of the pixels representing objects at a different location within the patch; d) assigning values to each of the plurality of pixels in one section of the map by selecting one of the pixels in the array of pixels, the selected pixel in the array representing a location on the ground closest to the location represented by the pixel in the map; and e) repeating steps a) through d) to assign values to pixels in other sections of the map. - View Dependent Claims (11, 12, 13, 14)
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15. A synthetic aperture radar apparatus comprising:
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a) means for transmitting chirped pulses with a chirp slope, S, and a pulse repetition interval, Tp ; b) means for receiving reflected radio signals of the transmitted pulses from an object; c) means for determining the range between the synthetic aperture radar and the object; and d) means, responsive to the range determining means, for changing the chirp slope, S, and pulse repetition period, Tp. - View Dependent Claims (16, 17)
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Specification