Synchronization algorithm for RFID-reader and its implementation

An algorithm for synchronization of a decoder of a RFID receiver has been proposed, implemented and evaluated, by experimental setup. The solution can be used for UHF RFID (e.g. ISO18000-6 and EPC gen 2) readers using FM0, bi-phase or differential Manchester decoding. Goal of the proposed solution is the improved decoding of the received data in the presence of noise (so by using less power or working at longer distance) by innovative synchronization techniques. Synchronization problem (and challenge) is caused by non-precise timing of the binary signals sent by simple passive RFID-tags. Hardware prototype has been developed for testing and evaluating of the RFID-reader synchronization algorithm for decoding of the binary information. The developed algorithm has been implemented as C/C++ code for DSP and can be evaluated, benchmarked and developed further, with real-world experimental data log files acquired with the developed hardware setup (also on PC). The proposed algorithm is based on the finding of the best correlation of the expected binary preamble (header) waveform of the communication packet with corresponding part of the received noisy signal, as used in other known solutions, with variation of the possibly expected timing parameters, e.g by using matched correlation (FIR) filter-banks. The idea of the proposed solution is to use additionally to maximum correlation of the received signal with the reference preamble waveform also the “quadrature” version of the reference (derived from the ideal preamble) signal, as the “quadrature” correlation has at the best match clear zero value and has change around this “zero” point. So using this additional “Q” correlation channel gives the opportunity to find the exact timing base (“bit duration”) more precisely. The proposed algorithm and the results of the evaluation of the solution with real-world data are described. Also, potential future developments of the solution are discussed.