RFID tag switched capacitor slicer threshold
AssigneeImpinj, Inc.
InventorJohn D. Hyde
Life of this patent
Estimating the term…
Abstract
An RFID tag that receives an RF signal from a reader is arranged to derive a threshold signal from a detected envelope of the RF signal, where the threshold signal is proportional to the detected envelope signal. The detected envelope signal is then compared to the threshold signal to derive a digital signal from the received RF signal. By maintaining the threshold signal proportional to the detected envelope signal, false bit detections due to ripple effect on the received signal and interference from other sources are reduced. The threshold signal may be derived employing a switched capacitor attenuator circuit.
Claims25
A demodulator circuit for an RFID tag, comprising:
- an envelope detector for deriving a first signal responsive to detecting an envelope of a received signal;
- an attenuator for attenuating a portion of the first signal to derive a second signal by repetitively charging a capacitor of the attenuator with the first signal, and then discharging the capacitor;
- a peak detector for deriving a threshold signal by detecting a peak of the second signal, wherein the threshold signal is proportional to the first signal;
- and
- a comparator for providing a digital signal in response to comparing the first signal and the threshold signal.
A demodulator circuit for an RFID tag, comprising:
- a means for deriving a first signal responsive to detecting an envelope of a received signal;
- a means for attenuating at least a portion of the first signal to derive a second signal;
- a means for deriving a threshold signal by detecting a peak of the second signal, wherein the threshold signal is proportional to the first signal;
- and
- a means for deriving a digital signal by comparing the first signal and the threshold signal.
A method for a demodulator circuit in an RFID tag, comprising:
- deriving a first signal responsive to detecting an envelope of a received signal;
- attenuating at least a portion of the first signal to derive a second signal;
- deriving a threshold signal by detecting a peak of the second signal, wherein the threshold signal is proportional to the first signal;
- and
- deriving a digital signal by comparing the first signal and the threshold signal.
Dependencies are inferred from the claim text.