Method and system for reading RFID tags

Abstract

A method and a system for reading radio frequency identification (RFID) tags are provided. The method includes the following steps. First, receive a tag signal from the RFID tag. Recover a data clock rate from the tag signal according to statistics of pulse lengths of the tag signal. Next, determine a frame synchronization point of a data frame following a preamble in the tag signal by a signal correlation between the preamble and a predetermined signal pattern according to the data clock rate. Finally, decode the data frame by using an adaptive Viterbi algorithm on an extended trellis diagram. The extended trellis diagram includes a plurality of nodes and a plurality of branches connecting the nodes. The nodes and the branches are arranged according to the modulation scheme of the data frame and possible variations of the data clock rate.

Dependencies are inferred from the claim text.