Off-axis indicator algorithm for electrically large antennas
AssigneeRaytheon Company
InventorsJerome H. Pozgay, Wesley T. Dull, Lawrence A. Durfee
Life of this patent
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Abstract
A technique is described which makes novel use of monopulse data to augment the normal CFAR detection processing by incorporating monopulse data in a computationally simple way into the detection decision process such that off-axis signals which are of sufficient strength to pass a CFAR detection threshold are effectively rejected by a second detection threshold. The signal compared to the second detection threshold is formed from all of the monopulse channels. Detection processing is thus a two step process, incorporating not only the information contained in the magnitude of the Sum channel, but information contained in all of the monopulse channels.
Claims15
A radar system comprising a system for use in a monopulse radar to determine whether a signal is arriving from a direction corresponding to the pointing direction of an antenna main beam, or from a direction corresponding to directions covered by antenna sidelobes, the system comprising:
- a first circuit to provide a signal indicative of information contained in all monopulse channels as well as signals indicative of information contained in each respective monopulse channel;
- and
- a second circuit to utilize the signals provided by the first circuit to eliminate off-axis detections with a relatively minor loss in mainlobe detection probability wherein the first and second circuits cooperate to incorporate monopulse data to reject off-axis signals which are of sufficient strength to pass a CFAR detection threshold.
A radar system comprising:
- an antenna having four quadrants, each quadrant capable of providing a signal having a magnitude indicative of signals received by said quadrant including a B1 signal, a B2 signal, a B3 signal and B4 signal, respectively;
- and
- a receiver, responsive to each of the signals B1, B2, B3 and B4, to provide a sum signal Σ having a magnitude which is equal to a sum of the magnitudes of the B1 signal, the B2 signal, the B3 signal and the B4 signal and an off axis indication signal I which is equal to {|B1−B2|+|B2−B3|+|B3−B4|+|B4−B1|}/|Σ|.
A radar system comprising:
- an antenna with monopulse arithmetic circuitry capable of providing a Σ signal, a Δaz signal, a Δel signal and a Q signal, each of the respective signals having a magnitude;
- and
- a receiver, responsive to the Σ signal, the Δaz signal, the Δel signal and the Q signal, to provide an off-axis indication signal, I, where the off-axis indication signal I is equal to a sum of the magnitudes of the Δaz signal, the Δel signal and the Q signal divided by the magnitude of the Σ signal.
A method of operating a monopulse radar system comprising the steps of:
- forming a sum signal, Σ, an azimuth difference signal, Δaz, an elevation difference signal, Δel, and a Q difference signal, Q, and obtaining magnitudes of each of the respective signals;
- comparing the magnitude of the azimuth difference signal, Δaz with the magnitude of the sum signal, Σ;
- comparing the magnitude of the elevation difference signal, Δel with the magnitude of the sum signal, Σ;
- comparing the magnitude of the Q difference signal, Q with the magnitude of the sum signal, Σ;
- summing each result of the comparing steps;
- and
- comparing the summed result with a threshold value to determine an off-axis indication.
A method of operating a monopulse radar system comprising the steps of:
- forming difference signals of the four possible combinations of contiguous beam pairs;
- comparing magnitudes of the differences to a sum pattern magnitude;
- and
- summing each result of the comparing step.
A method of operating a monopulse radar system comprising the steps of:
- forming a respective digital signal indicative of a signal from each quadrant of a monopulse antenna;
- forming a sum signal indicative of a combined signal from all quadrants of the monopulse antenna and deriving a magnitude of said sum signal;
- forming difference signals of each possible combination of signals from each quadrant of the monopulse antenna and deriving a magnitude of each of the respective difference signals;
- comparing the magnitude of each of the difference signals to a magnitude of the sum signal;
- and
- summing each result of the comparing step.
Dependencies are inferred from the claim text.