Patent ID: 7614556
Filing Date: 2009-11-10
Classification: G06K

Abstract:
1. A radio frequency identification (RFID) system, comprising: a plurality of RFID tags, each of the plurality of RFID tags including a linear polarized antenna for communicating an RFID tag signal; at least one receiver antenna for receiving the RFID tag signals, the receiver antenna including a circular polarized helical antenna element; an RFID tag signal reader coupled to the at least one receiver antenna that processes the RFID tag signals; a transmitter antenna for transmitting an RF signal to the RFID tag, the transmitter antenna including a circular polarized quadrifiler helical antenna element; and a transmitter coupled to the at least one transmitter antenna that generates the RF signal; wherein the RFID tag communicates the RFID tag signal in response to receiving the RF signal from the transmitter antenna; wherein the plurality of RFID tags include a first tag and a second tag, the transmitter antenna being configured to apply a first gain on axis to the first tag and a second gain to the side of axis to the second tag, where the second gain is greater than the first gain.