PILOT WARNING INDICATOR SYSTEM UTILIZING A TRANSMISSION OF SIGNALS WITHIN THE ABSORPTION BAND OF THE OXYGEN SPECTRUM

摘要

A proximity indicator system for aircraft which includes a radio signal transmitter having a predetermined output frequency range within an absorption band of the spectrum of a major invariable constituent of the atmosphere. A transmit antenna, which may be rotatable, is employed to propagate an output frequency within the predetermined range which may be responsive to variations in ambient atmosphere density and hence altitude. A rotatable antenna is connected to a radio receiver which has a predetermined amplitude threshold receiving level and is attuned to at least a portion of the output frequency range. A display is connected to the receiver to indicate reception of a signal and, optionally its direction. The output signal may be monitored by a receiver which contains a modulating circuit to compare a received signal with the monitored signal, the resultant being representative of any altitude differential which may exist between the respective signal sources. Resultants which represent more than a predetermined maximum differential will be rejected. A rotatable transmit antenna may supply bearing information regarding the output signal to a modulating circuit simultaneously with a signal representing air speed, whereby the output signal is impressed with a bearing velocity component. The output signal is monitored and compared with a similarly encoded received signal to reject information derived from a receding source (or other sources not representing a near term collision threat).