Open transmission line locating system.

摘要

An open transmission line system for locating an entity (703) within a defined pathway, in the presence of an alternating electromagnetic field extending in the vicinity both of said pathway and said mobile entity has an open transmission line (507; 701) adapted to extend along said pathway; and generating means (504; 704) coupled to said transmission line for producing and applying a driving signal to said transmission line; said transmission line including means (901; 1001; 1100) for receiving said electromagnetic field and producing therefrom a transmission signal which propagates along said transmission line; and means (1201; 1202) responsive to said driving signal for controlling the velocity of propagation of said transmission signal along said transmission line; said generating means including means (609) for varying said driving signal to vary the velocity of propagation of said transmission signal along said line, and signal processing means (503; 709) adapted to be coupled to one of said transmission line (701) and said mobile entity (703) for receiving said transmission signal and for determining, utilising the variation in the velocity of said transmission signal, the location of said mobile entity relative to said transmission line.