초록 ▼

A monopulse radar operating at low angles of elevation (LOE) receives returns from a target by a direct path and by a path including a reflection from that portion of the Earth's surface lying between the radar and the target. The surface-reflected signal tends to cause errors in the estimate of the

A monopulse radar operating at low angles of elevation (LOE) receives returns from a target by a direct path and by a path including a reflection from that portion of the Earth's surface lying between the radar and the target. The surface-reflected signal tends to cause errors in the estimate of the elevation of the target. A radar system directs at least upper and lower overlapping beams at LOE toward the target for receiving returns. The upper and lower beams may be sequential or simultaneous. Real and imaginary portions of the sum (Σ) and difference (Δ) signals are generated for each beam. The monopulse estimates of elevation �� derived from the real portion of the Σ and Δ signals are processed to produce correction signals for upper and lower beams. Each correction signal is weighted and summed to correct the estimate of elevation.

대표청구항 ▼

What is claimed is: 1. A method for determining the elevation of a target, comprising the steps of: transmitting electromagnetic energy toward the target; directing first and second antenna beams toward said target for reception of reflections of said electromagnetic energy, said first and second b

What is claimed is: 1. A method for determining the elevation of a target, comprising the steps of: transmitting electromagnetic energy toward the target; directing first and second antenna beams toward said target for reception of reflections of said electromagnetic energy, said first and second beams being angularly spaced in the vertical plane to produce a lower beam and an upper beam, said angular spacing in the vertical plane being about one-third of a 3 dB beamwidth of one of said upper and lower beams; forming an upper monopulse estimate of the elevation angle of said target from said upper beam; forming a lower monopulse estimate of the elevation angle of said target from said lower beam; multiplying said upper monopulse estimate by a first predetermined constant to form a first corrected estimate of the elevation of said target; multiplying said lower monopulse estimate by a second predetermined constant to form a second corrected estimate of the elevation of said target; and adding together said first and second corrected estimates to form a further estimate of the elevation of said target. 2. A method according to claim 1 wherein said step of directing said first and second antenna beams are performed concurrently, and said steps of forming upper and lower monopulse estimates are performed concurrently. 3. A method according to claim 1 wherein said steps of directing said first antenna beams and forming one of said upper and lower monopulse estimates are performed before said steps of forming said second antenna beam and the other of said upper and lower monopulse estimates. 4. A method according to claim 1 wherein said upper monopulse estimate includes real and imaginary portions, and said first predetermined constant is bipartite to include first and second portions, and said real portion of said upper monopulse estimate is multiplied by said first portion of said first predetermined constant to form a corrected real portion of said upper monopulse estimate, and said imaginary portion of said upper monopulse estimate is multiplied by itself to form an upper imaginary square, and said upper imaginary square is multiplied by said second portion of said first predetermined constant and added to said corrected real portion of said upper monopulse estimate to form said first corrected estimate of the elevation of said target. 5. A method according to claim 4 wherein said lower monopulse estimate includes real and imaginary portions, and said second predetermined constant is bipartite to include first and second portions, and said real portion of said lower monopulse estimate is multiplied by said first portion of said second predetermined constant to form a corrected real portion of said lower monopulse estimate, and said imaginary portion of said lower monopulse estimate is multiplied by itself to form a lower imaginary square, and said lower imaginary square is multiplied by said second portion of said second predetermined constant and added to said corrected real portion of said lower monopulse estimate to form said second corrected estimate of the elevation of said target. 6. A method according to claim 5 further comprising the steps of: forming the absolute value of the difference between said real portion of said upper monopulse estimate and said real portion of the said lower monopulse estimate to form an absolute first difference; multiplying the said absolute first difference by a predetermined constant to form a corrected absolute first difference; and adding said corrected first difference to said second corrected estimate of the elevation of said target. 7. A method according to claim 6 further comprising the steps of: forming the product of said real portion of said upper monopulse estimate with itself to form an upper first square; forming the product of said upper imaginary square with itself to form an upper second square; multiplying said upper first and second squares by predetermined first and second further constants, respectively, to form corrected upper first and second squares; and adding said corrected upper first and second squares to said second corrected estimate of the elevation of said target. 8. A method according to claim 7 further comprising the steps of: forming the product of said real portion of said lower monopulse estimate with itself to form a lower first square; forming the product of said lower imaginary square with itself to form a lower second square; multiplying said lower first and lower second squares by predetermined first and second further constants, respectively, to form corrected lower first and lower second squares; and adding said corrected lower first and lower second squares to said second corrected estimate of the elevation of said target. 9. A method according to claim 8 further comprising the steps of: multiplying said upper monopulse estimate by said lower imaginary square to form a first cross product; multiplying said real portion of said lower monopulse estimate by said upper imaginary square to form a second cross product; multiplying said real portion of said upper monopulse estimate by said real portion of said lower monopulse estimate to from a third cross product; multiplying said upper imaginary square by said lower imaginary square to form a fourth cross product' multiplying said upper first square by said upper imaginary square to from a fifth cross product; multiplying said lower first square by said lower imaginary square to form a sixth cross product; adding said first, second, third, fourth, fifth and sixth cross products at least to each other to form a further correction; and adding said further correction to said second corrected estimate of the elevation of said target.