| 摘要 |
An instrument landing system for determining the altitude of an aircraft at a plurality of points along a glide path defined by a plurality of spaced transmitters located along a ground reference line and transmitting at a predetermined frequency, the aircraft receiver apparatus comprising means for producing a pulse pair for each transmitter point corresponding to a predetermined Doppler frequency shift which is realized first when converging on the transmitter point and second when diverging from the transmitter point and means for determining altitude as a function of velocity and the time elapsed between the pulses of the pair. Altitude deviation from the glide path is determined by a comparison of signals related to the distance between two succeeding transmitter points and the time spacing of a pulse pair.
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