RADIO-FREQUENCY SIGNAL DETECTOR CIRCUIT FOR SEMI-PASSIVE RFID TAGS

摘要

A radio-frequency signal detector circuit for semi-passive RFID tags detects the presence of a radio-frequency signal emitted by the reader. The circuit has applications in semi-passive RFID tags, that is to say, circuits that are deactivated in the absence of a radio-frequency signal and activated when a radio-frequency signal is detected in order to establish communication with the reader. The circuits comprises two envelope detectors, one detector detects the upper envelope and the other the lower envelope. The upper and lower envelopes are compared by a comparator circuit with a sensitivity threshold, such that whenever the difference between the upper and lower envelopes is greater than the sensitivity threshold of the comparator, the radio-frequency signal is detected.