Patent ID: 8688140

Claim:
A method for locating a radio frequency tag using spatially separated beacon nodes, said method comprising the steps of: providing at least one beacon node comprising a plurality of antennas coupled with an antenna switch, a radio frequency device coupled with the antenna switch, and a microcontroller having outputs and at least one input, the microcontroller being coupled with the radio frequency device and with said antenna switch; transmitting a plurality of beacon symbols from cyclically selected antennas of each of a plurality of beacon nodes, wherein the microcontroller is configured to select an antenna by controlling said antenna switch through its outputs and wherein the radio frequency device provides timing pulses to the at least one input of the microcontroller which trigger the microcontroller to perform an antenna switch at a symbol boundary; receiving the plurality of beacon symbols at a radio frequency (RF) tag; determining phase jumps of the plurality of beacon symbols received at the RF tag and the respective selected antennas transmitting each of the plurality of beacon symbols for each of the plurality of beacon nodes; estimating an angle-of-arrival (AoA) of the plurality of beacon symbols transmitted from each of the plurality of beacon nodes; estimating an AoA vector for each of the plurality of beacon nodes from the respective AoA estimates; and estimating a spatial location of the RF tag from the AoA vectors.