| 摘要 |
An elevation angle detection device uses signals from first and second of oppositely pointing antennas to determine an elevation angle of an emitting source. The signal from the second antenna is inverted and phase-compared with the direct signal from the first antenna. The first and second antennas are physically displaced along their axes by about ⅜ electrical wavelengths to establish a sensitive angular region of about ±7 degrees. In one embodiment of the invention, the phase of the signal from the first antenna is phase delayed slightly before being applied to the phase detector. This displaces the sensitive angular region upward. The phase of the signal from the second antenna is phase delayed slightly before being applied to a second phase detector. The signal from the first antenna is applied to the second phase detector without being phase delayed. This displaces the sensitive angular region downward. The sensitive angular regions produced by the first and second phase detectors overlap centered on a plane normal to the axes of the first and second antennas. The simultaneous presence of an emitter in the overlap is used to detect a crisis collision possibility.
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