Precision approach sensor system for aircraft

摘要

A microwave interrogation-transponder system for controlling the airborne rendezvous and closure of two aircraft for aerial refueling and the like. The system of the invention includes a microwave interrogator mounted on the aft underfuselage of a tanker aircraft, for example, for interrogating and receiving a reply from a small microwave transponder mounted on the receiver aircraft near the aerial refueling receptacle. The angle of the received signal relative to the tanker is obtained from the angle sensing receiver portion of the microwave interrogator; whereas range is obtained from the phase of the returned modulation tone (i.e., a range tone) relative to that which was transmitted by the interrogator. The transponder sends back to the interrogator a signal which is shifted in frequency with respect to the transmitted signal and operates in an active mode with gain at long ranges and in a passive mode with no gain at shorter ranges to achieve extremely accurate guidance characteristics.