LOW ANGLE RADAR TRACKING SYSTEM
First Claim
1. In a method for determining by radar the elevation angle of a target which is at a relatively low altitude so that both direct and reflected radar signals are returned to the radar site, the steps of receiving said direct and reflected radar signals On a pair of directional beams which have patterns and are orientated such that their ratio has even order symmetry with respect to a horizontal axis;
- and determining the ratio of the signals received on said pair of directional beams, said ratio being indicative of said elevation angle.
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Abstract
The elevation angle of a target which is at a low altitude over a reflecting surface is ascertained by receiving both direct and reflected radar signals on a pair of fixed directional beams which have patterns such that their ratio has even order symmetry about a horizontal axis. The ratio of the total signals received on these beams is indicative of this angle.
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Citations
8 Claims
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1. In a method for determining by radar the elevation angle of a target which is at a relatively low altitude so that both direct and reflected radar signals are returned to the radar site, the steps of receiving said direct and reflected radar signals On a pair of directional beams which have patterns and are orientated such that their ratio has even order symmetry with respect to a horizontal axis;
- and determining the ratio of the signals received on said pair of directional beams, said ratio being indicative of said elevation angle.
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2. In a method as defined in claim 1 wherein the ratio of said beam patterns has a parabolic shape.
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3. In a method as defined in claim 2 wherein the square root of the ratio of the signals is determined.
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4. In a method as defined in claim 1 wherein one of said directional beams is squinted upwardly with respect to said horizontal axis so as to discriminate in favor of the direct signal arriving at said radar site.
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5. In a method for determining the elevation angle of a target which employs radar and wherein direct and reflected radar signals arrive back at the radar site, the steps of forming a pair of directional beams in space which have patterns that over their main beam areas have even order symmetry with respect to an axis;
- orientating said directional beams such that this axis is horizontal;
receiving both the direct and reflected radar signals from said target on this pair of beams; and
measuring the ratio of the signals so received, said ratio being indicative of the elevation angle.
- orientating said directional beams such that this axis is horizontal;
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6. In a method as defined in claim 5 wherein each value of the ratio corresponds to only one positive value in the main beam region.
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7. Apparatus for determining the elevation angle of a low altitude target which is above a reflecting surface so that radar signals striking said target produce direct and reflected radar signals back at the radar site, the combination of means for forming a pair of directional beams which have patterns such that over the main beam regions the ratio of these patterns has even order symmetry with respect to a horizontal direction;
- means for receiving said direct and reflected radar signals on each beam; and
means for measuring the ratio of the signals so received, said ratio providing an indication of the elevation angle.
- means for receiving said direct and reflected radar signals on each beam; and
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8. In an arrangement as defined in claim 7 wherein the ratio of said patterns has a parabolic shape;
- and means for obtaining the square root of the ratio of the radar signals.
Specification