Patent ID: 6943680

Claim:
A radio frequency identification system, interrogator, comprising: a first antenna adapted to generate a first magnetic field component having a first phase; a second antenna adapted to generate a second magnetic field component having a second phase; a driver circuit coupled to the first and second antennae to provide at least one signal to cause the generation of first and second magnetic field components; whereby a first and second magnetic fields form a time varying composite magnetic field; a detector for detecting a transponder signal modulated on said magnetic field; a processor for processing the transponder signal; and wherein said processor further comprises: at least one potentiometer coupled to said detector and adapted to nullify interference on said detected signal; an amplifier coupled to said at least one potentiometer and adapted to amplify said detected signal; a filter coupled to said amplifier and adapted to filter said detected signal; a demodulator coupled to said filter and adapted to demodulate said detected signal; at least one decoder coupled to said demodulator and adapted to decode said demodulated signal; and a signal processor coupled to said at least one decoder and adapted to process said decoded signal.