Data recovery system for radio frequency identification interrogator

Abstract

An RF/ID interrogator is provided for recovering a data signal from an RF/ID tag. The interrogator includes a radio having a receiver portion to receive in-phase (I) and quadrature-phase (Q) signals from the RF/ID transponder transmitted at a predetermined bit-rate, and a processor coupled to the radio for controlling operation of the radio in accordance with stored program instructions. In one embodiment, the interrogator performs over-sampling of the data signal received from the RF/ID tag in order to provide a high data recovery rate. The processor controls the over-sampling of the I and Q signals at a sampling rate higher than the transmitted bit-rate of the I and Q signals to provide plural signal samples that are stored in a buffer memory. The processor compares the relative polarity of successive ones of the plural signal samples. Based on this comparison, data bits are derived from the successive ones of the plural signal samples in correspondence with the number of the successive ones of the plural signal samples having same relative polarity. In another embodiment, the interrogator performs a selection between the I and Q signals in order to achieve optimum data recovery. The processor detects relative signal strength of the I and Q signals, and selects one of the I and Q signals for subsequent processing based on the detected relative signal strength. Data bits are then recovered from the selected one of the I and Q signals.