Systems and Methods for Tracking Objects Using Magnetoresistance

A position transponder configured to operate inside a body of a subject, the transponder comprising:

• a sensor coil, coupled so that a voltage drop is induced in the sensor coil when one or more electromagnetic fields is applied to the body of the subject containing the transponder, the one or more electromagnetic fields being applied from one or more transmitters external to the body;
• a magnetoresistive device coupled to the sensor coil in series via a single twisted pair or a coaxial cable, such that a voltage drop is induced in the magnetoresistive device responsive to the electromagnetic fields applied to the body;
• and
• a control unit, coupled to the sensor coil and the magnetoresistive device so as to generate an output signal indicative of the voltage drop induced at the sensor coil and the voltage drop induced at the magnetoresistive device, such that the output signal is indicative of coordinates of the transponder inside the body.

A tracking system for tracking an object, comprising:

• a radio frequency driver transmitting a radiofrequency driving current at a first frequency to the object;
• a plurality of transmitters adapted to generate electromagnetic fields at different respective frequencies, including a second frequency, located external to the object;
• a transponder within the object, the transponder comprising:
• a sensor coil, the sensor coil configured to sense a voltage drop in response to exposure to the electromagnetic fields;
• a magnetoresistive device coupled to the sensor coil in series via a single twisted pair or a coaxial cable, such that the magnetoresistive device is adapted to sense the electromagnetic field at a direction substantially perpendicular to the axis of the sensor coil and thereby experience a voltage drop;
• and
• a control unit coupled to the sensor coil and the magnetoresistive device, so as to generate an output signal indicative of the voltage drop induced at the sensor coil and the voltage drop induced at the magnetoresistive device;
• and
• a signal processing unit separate from and coupled to the transponder, the signal processing unit adapted to receive the output signal transmitted by the control unit and responsive thereto to determine the coordinates of the object.

A method for tracking an object, comprising:

• positioning a radio frequency (RF) driver to transmit an RF driving current at a first frequency, to the object located within a body of a subject;
• coupling to the object a transponder comprising a sensor coil and a magnetoresistive device that are connected using a single twisted pair or a coaxial cable;
• driving a plurality of transmitters external to the body to generate electromagnetic fields at respective frequencies in a vicinity of the object that induce a voltage drop across the sensor coil and the magnetoresistive device;
• generating an output signal at the transponder indicative of the voltage drop across the sensor coil and the voltage drop across the magnetoresistive device;
• transmitting the output signal from the transponder;
• and
• receiving and processing the output signal to determine coordinates of the object within the body.