Patent ID: 7385477

Claim:
A radio frequency identification system comprising: a host computer including an application program to control an interrogator and to receive data from the interrogator; a plurality of interrogators, including the interrogator coupled to the host computer and configured to transmit a forward link signal to implement an arbitration scheme to determine an identification code of an RFID tag from among a plurality of RFID tags contained within an RF field of the interrogator, the forward link signal comprising an RF carrier that is modulated using amplitude shift keying to provide a first parameter, a second parameter, a third parameter, a CRC, and return link configuration information; an item of inventory having affixed thereto a label comprising identifying text; and the RFID tag disposed on plastic substrate and laminated to a back side of the label to track the item via the host computer, the tag comprising a dipole antenna and no more than one monolithic integrated circuit storing an identification code associated with the item and configured to switch between a plurality of available modulation schemes, the tag configured to receive the signal via the dipole antenna, to store the first parameter, to compare the second parameter to a value stored in the integrated circuit other than the identification code, to generate a random number, to compare the third parameter to the first parameter, and to communicate a reply to the signal via the dipole antenna depending, at least in part, on whether the third parameter matches the first parameter and whether the second parameter matches the value, the reply comprising a return link signal modulated in accordance with a modulation scheme selected by the return link configuration information, wherein in accordance with one of the plurality of modulation schemes each bit of the return link signal is multiplied by a selectable one of at least three subcarrier sequences selected by the return link configuration information.