Monopulse radar system
First Claim
1. In a monopulse radar system comprising fixedly-mounted antenna means having a given axis for simultaneously picking up a respective signal from each member of a set of discrete spaced electromagnetic beam components disposed substantially symmetrically about said axis, and means coupled to said antenna means for utilizing predetermined sum and difference signals of said respective picked-up signals;
- the improvement wherein said system includes axis-rotating means coupled to said utilizing means which in effect rotates said set of beam components about said axis through any given angle by combining certain of said signals in accordance with predetermined transformation functions of said given angle to obtain the effect of rotation of said axis through said given angle, wherein said set includes four beam components spatially distributed about said axis in the form of a square, whereby the position of each beam component corresponds with a different vertex of said square with the vertices corresponding to first and second ones of said beam components defining a first side of said square, and vertices corresponding to third and fourth ones of said beam components defining a second side of said square, the vertices corresponding to said first and third ones of said beam components defining a third side of said square, and the vertices corresponding to said second and fourth ones of said beam components defining a fourth side of said square;
wherein said utilization means includes means for deriving a summation signal equal to the sum of the picked-up signals of all said four beam components, a first difference signal equal to the difference between the sum of picked-up signals of said first and second beam components and the sum of picked-up signals of said third and fourth beam components, and a second difference signal equal to the difference between the sum of the picked-up signals of said first and third beam components and the sum of the picked-up signals of said second and fourth beam components, and wherein said transformation functions are defined by the following formula;
1 Δ
A'"'"' = Δ
A cos - Δ
B sinθ
2 Δ
B'"'"' = Δ
B sin + Δ
B cosθ
;
where Δ
A is said first difference signal, Δ
B is said second difference signal, θ
is said given angle of rotation;
Δ
A'"'"' is a rotated first difference signal and Δ
B'"'"' is a rotated second difference signal.
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Abstract
Structure, such as a variable coupler, is employed to effectively rotate monopulse beam components through any given angle about the monopulse antenna axis. Useful in an airborne velocity measuring doppler radar, where servo means control the value of the given angle so that the rotated beam components are maintained properly aligned with an isodop, despite aircraft drift.
19 Citations
4 Claims
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1. In a monopulse radar system comprising fixedly-mounted antenna means having a given axis for simultaneously picking up a respective signal from each member of a set of discrete spaced electromagnetic beam components disposed substantially symmetrically about said axis, and means coupled to said antenna means for utilizing predetermined sum and difference signals of said respective picked-up signals;
- the improvement wherein said system includes axis-rotating means coupled to said utilizing means which in effect rotates said set of beam components about said axis through any given angle by combining certain of said signals in accordance with predetermined transformation functions of said given angle to obtain the effect of rotation of said axis through said given angle, wherein said set includes four beam components spatially distributed about said axis in the form of a square, whereby the position of each beam component corresponds with a different vertex of said square with the vertices corresponding to first and second ones of said beam components defining a first side of said square, and vertices corresponding to third and fourth ones of said beam components defining a second side of said square, the vertices corresponding to said first and third ones of said beam components defining a third side of said square, and the vertices corresponding to said second and fourth ones of said beam components defining a fourth side of said square;
wherein said utilization means includes means for deriving a summation signal equal to the sum of the picked-up signals of all said four beam components, a first difference signal equal to the difference between the sum of picked-up signals of said first and second beam components and the sum of picked-up signals of said third and fourth beam components, and a second difference signal equal to the difference between the sum of the picked-up signals of said first and third beam components and the sum of the picked-up signals of said second and fourth beam components, and wherein said transformation functions are defined by the following formula;1 Δ
A'"'"' = Δ
A cos - Δ
B sinθ2 Δ
B'"'"' = Δ
B sin + Δ
B cosθ
;where Δ
A is said first difference signal, Δ
B is said second difference signal, θ
is said given angle of rotation;
Δ
A'"'"' is a rotated first difference signal and Δ
B'"'"' is a rotated second difference signal.
- the improvement wherein said system includes axis-rotating means coupled to said utilizing means which in effect rotates said set of beam components about said axis through any given angle by combining certain of said signals in accordance with predetermined transformation functions of said given angle to obtain the effect of rotation of said axis through said given angle, wherein said set includes four beam components spatially distributed about said axis in the form of a square, whereby the position of each beam component corresponds with a different vertex of said square with the vertices corresponding to first and second ones of said beam components defining a first side of said square, and vertices corresponding to third and fourth ones of said beam components defining a second side of said square, the vertices corresponding to said first and third ones of said beam components defining a third side of said square, and the vertices corresponding to said second and fourth ones of said beam components defining a fourth side of said square;
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2. In a doppler radar system aboard an aircraft of the type employing at least three non-coplanar beam antennas directed towards the ground for receiving return signals from the ground in response to transmitted radar signals and means responsive to said return signals for determining the velocity components of said aircraft with respect to the ground;
- the improvement wherein said antennas are fixedly mounted, non-track stabilized monopulse antennas having given respective axes with respect to said aircraft, each monopulse antenna simultaneously picking up a respective signal from each member of a set of discrete spaced beam components disposed substantially symmetrically about that antenna'"'"'s axis, and wherein said system includes axis-rotating means for each of said antennas responsive to said signals picked-up by that antenna which without any mechanical movement of said fixedly mounted, non-track stabilized monopulse antennas in effect rotates its set about its axis to maintain substantially constant at a predetermined value the angular orientation of its set with respect to an isodop on the ground.
- View Dependent Claims (3, 4)
Specification