Fast carrier cancellation for UHF near field RFID systems

A novel carrier cancelation circuit is presented for ultra high frequency (UHF) near field radio frequency identification applications. A directional coupler, logarithmic detector and controlling circuit are used for improving the sensitivity of the receiver. The cancelation circuit, which consists of vector multiplier and SCM (Single Chip Micyoco), can be adaptively tuned to generate an optimum canceling signal for carrier cancelation. In order to secure good and fast carrier cancelation, logarithmic detector is used as a feedback component to transmit power information of the tag signal channel. The implemented reconfigurable carrier cancelation exhibits good performance on reduction of carrier level in tag signal channel when the adaptive control voltage of SCM is applied. Furthermore, the carrier cancelation control system could be operated real time as well as applied for hopping-frequency systems.