ADAPTIVE ECHO CANCELLATION FOR RFID SYSTEMS

摘要

A radio-frequency identification (RFID) reader having fast-adaptive echo cancellation for backscatter-modulated signals is described. The echo cancellation includes subtracting an RF-level cancel signal from the received signal, where the cancel signal is generated based upon an error measured in the receive signal after down-conversion to baseband and low-pass filtering. The cancel signal is based upon a cumulative sum or integral of error signals and an estimated complex-valued transfer function of the scaling circuit. Methods of quick calibration of the reader are described, including accounting for circuit offsets and determining the estimated complex-valued transfer function.

主权项

1. A method for echo cancellation in a reader for a passive RFID system, comprising:
transmitting a carrier signal and receiving a backscatter-modulated signal; combining a cancel signal with the backscatter-modulated signal to obtain a corrected signal; downconverting the corrected signal to a baseband signal using the carrier signal; low-pass filtering the baseband signal to remove modulated transponder information and produce an error signal; and updating the cancel signal, wherein the cancel signal is based upon the error signal, the carrier signal, and an estimated complex-valued transfer function.