Patent ID: 7760132

Claim:
An RF system for finding a target in three dimensional space, comprising: a slave unit configured as a transponder; a monitoring unit configured as a transceiver for monitoring a location of the slave unit; a Radio Frequency (RF) communication system for communication between the slave unit and the monitoring unit and configured to transmit a ranging signal to the slave unit, the slave unit responding to the ranging signal by transmitting a reply ranging signal, the RF communication system further comprising a processor configured to repeatedly determine values for the position information of the slave unit based on (a) a transmission interval between the monitoring unit and the slave unit being an elapsed time between transmitting the ranging signal and receiving the reply ranging signal, (b) a calibration interval between each of the monitoring unit and the slave unit and being a time interval of a period to normalize circuitry of the monitoring unit and the slave unit, (c) an antenna propagation interval of the monitoring unit and the slave unit being an elapsed time of a signal measured as it passes through antennas of the monitoring and slave units, and (b) a measured distance between the monitoring unit and the slave unit in three dimensional space, determined by a spherical virtual triangulation relationship when successive values of the position information have a logical relationship relative to the previous values between the monitoring unit and slave unit.