Patent ID: 7924160

Claim:
A system for detecting tile location of an object ill three-dimensional space comprising, in combination, one or more transmitting stations for periodically transmitting electromagnetic signals, a surface wave acoustic transducer attached to said object, said transducer comprising: an antenna for capturing electrical energy from said electromagnetic signals received from said one or more transmitting stations, a piezoelectric substrate, a first set of conductive elements attached to the surface of said piezoelectric substrate and coupled to said antenna for converting said electrical energy into a surface acoustic wave that propagates across the surface of said substrate, a second set said conductive elements attached to the surface of said piezoelectric substrate and positioned in a path of travel of said acoustic surface wave for reconverting said acoustic wave into a modified electrical signal having a modified wave shape that uniquely identifies said transducer, for transmission back to said one or more transmitting stations as an electromagnetic signal, a third set of conductive elements attached to the surface of said piezoelectric substrate and positioned in a path of travel of said acoustic surface wave for converting said acoustic wave into a control signal that occurs before said modified electrical signal is produced by said second set of conductive elements, a normally unpowered amplification circuit having a signal input connected to said second set of conductive elements for amplifying said modified electrical signal as transmitted from said transducer to one or more receiving stations, and a switching circuit responsive to said control signal for supplying electrical power to said amplification circuit before and during occurrence of said modified electrical signal, and a signal processing system for determining the position of said transducer in three-dimensional space by measuring the distance separating said transducer from one or more receiving stations or by measuring the angle-of-arrival of said modified electromagnetic signal as it is received at one or more receiving stations, and calculating said position based on said distance or said angle-of-arrival or both.