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

Abstract

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

A Passive UHF RFID System Over Ethernet Cable for Long Range Detection

“…13). In other similar leakage cancellation designs, the demonstrated scanning times found in [16] and [17] were 43 ms and 330 ms respectively, and their leakage cancellation level ranged from 40 dB to 55 dB respectively under different leakage levels and settling times. However, in these studies, no tag detection results are presented.…”

“…Signals in the Cat5e Ethernet cable destructive interference occurs leaving only the backscattered tag signal. Several other leakage cancellation studies have utilized this methodology for RFID system [16][17][18].…”

Automatic leaking carrier canceller adjustment techniques

“…As long as the power detector is strictly monotone and the step width is chosen small enough to ensure stability, the algorithm will converge to the optimum LCC setting point. Few authors explicitly state adjustment algorithms, but the authors in [16] are using a gradient-based approach as well as in [12], who describe a similar approach and use a variable step width.…”

“…This demands for receivers with very large dynamic ranges, which enhance costs, both on the analog front end as well as on the analog to digital converters. To reduce these demands, many authors [6,[8][9][10][11][12][13][14][15][16][17] as well as commercial monolithic RFID reader chip manufacturers [18,19] propose or use active leakage cancellation techniques. These techniques, which originate in radar [20,21], extract a part of the transmit signal, adjust it in amplitude and phase and inject it at the receiver.…”

Design and development of ultra wide band transmitter leakage and reflected power canceller

“…These RPCs' uses quadrature feedback method to cancel the reflected signal. Recently various adaptive reflected power cancellers have been proposed to achieve optimal leakage cancellation in Radio Frequency Identification (RFID) readers [8][9][10]. However in all these approaches, the isolation bandwidth is limited.…”