Wireless identification and tracking using magnetic fields

An apparatus for locating a remote station, comprising:

• a magnetic field generator;
• a receiver for receiving a signal from a remote station indicative of a distance between the base station and the remote station;
• and
• a processor, coupled to the magnetic field generator and the receiver, the processor communicatively coupled to a memory having instructions for commanding the processor to compute the distance from the remote location to the base station from the received signal;
• wherein
• the magnetic field generator generates a time-varying magnetic field according to HT(t);
• and
• the signal is transmitted from the remote station when an intensity of the time-varying magnetic field measured at the remote station exceeds a threshold;
• and
• wherein the instructions comprise a module for determining the distance from the base station to the location of the remote station as proportional to a function f ⁡ ( H T ⁡ ( t thresh ) H R thresh ) , ⁢
• wherein HT(tthresh) is a magnitude of the magnetic field at the base station at tthresh and HRthresh is the magnetic field threshold.

An apparatus for locating a remote station, comprising:

• means for generating a magnetic field at a base station;
• means for receiving a radio signal transmitted from the remote station disposed at a location in response to the magnetic field;
• means for determining the distance from the base station to the location from the received radio signal transmitted from the remote station;
• wherein
• the magnetic field is time varying according to HT(t);
• the radio signal is transmitted from the remote station when an intensity of the time-varying magnetic field measured at the remote station exceeds a threshold;
• and
• the means for determining the distance from the base station to the location from the received radio signal comprises means for determining the distance from the base station to the location from the time the radio signal is received at the base station.