Implementation of an adaptive leakage cancellation control for passive UHF RFID readers

In this paper the implementation of an automatic leakage cancellation for UHF (Ultra High Frequency) RFID (Radio Frequency Identification) readers is presented. The system architecture and the control algorithms are described in detail. The proposed architecture has been completely implemented and measurements have been carried out for evaluation. The system is demonstrated to adaptively change the control signals to achieve an optimal leakage cancellation for every situation. It is shown that the Control Module keeps the leakage cancellation level between 41 dB and 46 dB, despite the leakage properties being changed by means of a phase shifter. It is also demonstrated that without such a module, the leakage power increases exponentially as the leakage properties change; e.g. from −41 dBm to −3 dBm with 30° phase shift. Finally, the system time response has been measured and the system operation has been evaluated in a reflective environment.