A low-cost software-defined UHF RFID reader with active transmit leakage cancellation

A monostatic UHF RFID reader targeting personal applications based on recently introduced commercial-off-the-shelf (COTS) software-defined radio (SDR) application-specific integrated circuits (ASICs) and field-programmable gate arrays (FPGAs) is proposed. The result is an RFID reader architecture whose principal components cost less than half of those of existing readers, but is flexible as a result of the programmable nature of the FPGA. The reader implements all mandatory EPC Gen 2 commands (except kill) and can perform inventory, targeted programming, blank tag programming, and singletag analysis via a smartphone interface. The proposed RFID reader architecture adaptively cancels the large CW transmit signal using a reflected power canceller (RPC). The RPC is terminated by a novel subranging tunable microwave network comprising digitally tunable capacitors capable of attenuating transmit leakage at the receiver by over 50dB. The reader achieves -73dBm of sensitivity at the antenna port when attached to a channel model and connectorized tag and achieves an open area tag read range of 2.6m with a 1.2dBi dipole antenna and 15.2m with a 12.5dBi patch antenna.