Patent ID: 8258923

Claim:
A method for locating a transponder (MT) with a remote locator (RL), the method comprising: selecting an identification code (ID Code) for transmission from the RL to at least one MT, wherein each of the at least one MT has a specific associated ID Code; generating, at a predetermined carrier frequency, a transmission signal for transmission by the RL, the transmission signal comprising: a first pattern that is transmitted over a first transmission interval, wherein the selected ID Code is encoded within the first pattern; transmitting the transmission signal from the RL for reception by the MT at a first time; receiving the transmission signal from the RL by the MT to provide a received signal; correlating, by FFT processing at the predetermined carrier frequency, the received signal with an ID Code stored in the MT to detect the presence of the selected ID Code in the received signal; upon detection of the selected ID Code in the received signal, generating an acknowledgement signal; transmitting the acknowledgement signal, at the predetermined carrier frequency, from the MT to the RL; said selected ID Code being encoded in the acknowledgement signal; receiving the acknowledgement signal from the MT by the RL at a second time; correlating, by FFT processing at the predetermined carrier frequency, the received acknowledgement signal with the selected ID Code stored in the RL to detect the presence of the selected ID Code in the acknowledgement signal; and upon detection of said selected ID Code in the acknowledgement signal, determining a distance between the RL and the MT as a function of an elapsed time between the first time and the second time.