| 摘要 |
System for tracking a vehicle equipped with a transponder which emits a first reply signal containing data identifying the vehicle in response to a first interrogation signal and emits a second reply signal containing data specifying the altitude of the vehicle in response to a second interrogation signal, the system including: (a) a squitter transmitter located on the vehicle for interrogating the transponder with the first and the second interrogation signals which are separated in time by a predetermined time spacing interval, in response to which first and second interrogation signals, the transponder transmits the first and second reply signals; (b) a plurality of spaced apart ground receive stations, each of which includes a receiver and decoder for: (i) receiving and decoding data from the first and second reply signals, (ii) determining a time of arrival of the first and second reply signals and the predetermined time spacing interval, and (iii) determining an identity of the vehicle by combining data from the first reply signal with information derived from the predetermined time spacing interval; (c) a communications link for connecting the ground receive stations with one of the ground receive stations; and (d) a computer at the one of the ground receive stations for receiving information from the other ground receive stations over the communication link, the information including the identity and time of arrival data determined from the time of arrival of the first and second reply signals, and for calculating the position of the vehicle from the time of arrival data. |
