Patent ID: 7917155

Claim:
A method for determining the relative position of a cooperative transponder by the use of a software defined radio transceiver in a personal electronic device, wherein the primary function of the software defined radio set is that of a cellular telephone, the method comprising: receiving a user initiated input that is indicative of a mode selection to a locator mode in the personal electronic device; executing a radio set configuration logic with a processor in the personal electronic device such that the processor reconfigures the software defined radio transceiver from a cellular telephone mode to a locator mode, wherein the software defined radio set and the processor in the personal electronic device are arranged to operate the locator mode by: selecting a target ID associated with the cooperative transponder; coding a sequence for the selected target ID; initiating the transmission of a structured multi-frame transmission to the cooperative transponder over a first time interval with the software defined radio set; capturing sample of a signal spectrum over a second time interval that is subsequent to the first time with the software defined radio set; correlating the captured samples over a third time interval with the software defined radio set; detecting a valid reply from the cooperative transponder device when the captured samples correlate to a structured reply transmission from the cooperative transponder with a reply cadence and frequency that substantially matches the expected reply cadence and frequency based on the internal clock of the personal electronic device; and determining a round-trip time-of-flight between the transmission of the structure multi-frame transmission and the detected valid reply.