AC-coupled RFID system
AssigneeClairvoyant Technology LLC
InventorThomas Frederick
Life of this patent
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Abstract
An AC-coupled RFID system is disclosed. Embodiments of the invention statistically correlate the transmit data from a baseband transmit signal and the receive data in a receive signal after the signal has passed through a baseband receive filter. By using a receive bandpass or high-pass filter at baseband, the receiver can be AC-coupled in the baseband. This AC coupling significantly reduces cost and complexity by eliminating high-power reflected signals at and near DC. The high-pass corner frequency of the receive filter passes enough of the receive signal to still be measurable. The correlation is used to estimate the reflected carrier, which in turn enables cancellation of the carrier, improving RFID reader sensitivity.
Claims26
A system for reading RFID tags, the system comprising:
- a transmit path to produce a transmit signal;
- a receive path to demodulate a tag signal produced in response to the transmit signal;
- a baseband receive filter to AC-couple a signal in the receive path to produce an AC-coupled receive signal;
- and
- a carrier estimator connected to the receive path and the transmit path to estimate at least one of an amplitude and a phase of a reflected carrier based on the transmit signal and the AC-coupled receive signal.
Apparatus for processing RFID signals, the apparatus comprising:
- means for estimating an amplitude of a reflected carrier to produce a carrier estimate;
- means for AC-coupling a receive signal so that the means for estimating can determine the amplitude based at least in part on a transmit signal and the receive signal;
- and
- means for cancelling the reflected carrier in the receive signal using the carrier estimate.
A method of cancelling a carrier signal from a receive signal in an RFID system, the method comprising:
- AC-coupling the receive signal including a reflected carrier through a baseband receive filter to produce a filtered receive signal;
- estimating at least an amplitude for the reflected carrier using a transmit signal and the filtered receive signal to produce a carrier estimate;
- and
- using the carrier estimate to cancel the carrier signal.
Dependencies are inferred from the claim text.