| 摘要 |
Blade tracker apparatus for tracking rotating helicopter blades includes an antenna which transmits a signal beam in the direction of the rotating blade. The impedance of the antenna changes as one of the blades enters the transmission beam and the amount by which the impedance changes varies as a function of the physical distance between the antenna and the blade. The varying impedance caused by a blade passing the antenna will amplitude modulate the transmitted signal and provide an indication of the distance of each of the several blades of a rotor as each of the blades passes through the field of the antenna.
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