Patent ID: 7397364

Claim:
A method for tracking an object, comprising: positioning a radio frequency (RF) driver to radiate an RF driving field toward the object; fixing to the object a wireless transponder comprising a power coil and at least one sensor coil; receiving the RF driving field using the power coil and storing electrical energy derived therefrom; driving a plurality of field generators to generate electromagnetic fields at respective frequencies in a vicinity of the object that induce a voltage drop across the at least one sensor coil; generating a digital output signal at the wireless transponder indicative of the voltage drop across the sensor coil, and powering the generation of the digital output signal using the stored electrical energy; transmitting the digital output signal from the wireless transponder using the power coil, and powering the transmission of the digital output signal using the stored electrical energy; and receiving and processing the digital output signal to determine coordinates of the object; wherein receiving the RF driving field comprises receiving the RF driving field: (a) during a first time period, prior to driving the plurality of field generators, and (b) during a second time period, subsequent to the first time period and prior to transmitting the digital output signal, wherein storing the electrical energy derived from the RF driving field comprises storing a first electrical energy during the first time period and storing a second electrical energy during the second time period, wherein powering the generation of the digital output signal comprises powering the generation of the digital output signal using the first stored electrical energy, and wherein powering the transmission of the digital output signal comprises powering the generation of the digital output signal using the second stored electrical energy.