Patent ID: 6100840
Filing Date: 2000-08-08
Classification: G01S,G06K,H01Q

Abstract:
A radio frequency tag system comprising an interrogator and a tag, wherein said tag is secured to an object and wherein:said interrogator is configured to generate a transmitted electromagnetic interrogation signal at a predetermined interrogation frequency;said tag comprises an antenna array including a plurality of receiver antennas and a plurality of transmitter antennas;said tag is positioned to receive said interrogation signal at said receiver antennas and is operative to return a reflected signal to said interrogator via said transmitter antennas in response to receipt of said interrogation signal;said tag is configured to generate said reflected signal bysuppressing reflection of said interrogation signal, andgenerating reflected radiation characterized by a frequency spectrum including a plurality of return bands, each of said return bands being characterized by a predetermined return band frequency; andsaid interrogator is configured to detect radiation reflected at said return band frequencies, discriminate between return bands of different frequencies, and identify a binary code defined by said reflected radiation across said plurality of return bands.