UHF RFID reader with separate central frequencies for forward and reverse links

Abstract

In a passive ultra high frequency radio frequency identification (UHF RFID) system, the reverse link (tag to reader) transmission is realized by the backscattering approach. Traditional UHF RFID readers use the same carrier frequency for both the forward and reverse links. In this paper, a UHF RFID reader that uses different central frequencies for the forward and reverse links is presented. Since the two links are separated in the frequency domain, a new channelization scheme is realized to accommodate twice as many readers in the same bandwidth as the traditional channelized signaling. The new reader adopts a heterodyne transmitter with a digital IF architecture instead of the commonly used homodyne transmitter and therefore, significantly reduces the complexity of the RF/analog section of the reader. Some measured results of the prototype system are shown in this paper to prove the validity of our method.