Interference cancellation in RFID systems
First Claim
1. A circuit for canceling an interference signal, the circuit comprising:
- a receive path that includes a downconverter, the downconverter to output a first signal related to the interference signal;
a canceller to output a second signal that is related to the first signal; and
a first coupler to couple the second signal into the receive path before the downconverter.
2 Assignments
0 Petitions
Accused Products
Abstract
An interference canceller for a RFID reader senses a signal related to the interference signal in the receive path of the reader. The canceller outputs an adjustment signal that depends on the sensed signal, which is coupled into the receive path before a downconverter in the receive path. The canceller can use a signal derived from the transmit path in generating the adjustment signal. The canceller adjusts the amplitude or phase (or both) of the derived signal to form the adjustment signal so that it cancels a carrier feed-through interference signal when injected into the receive path. The canceller can include a vector modulator to adjust the amplitude and/or phase of the derived signal; or alternatively, the canceller can include a variable attenuator and a variable phase shifter to adjust the amplitude and/or phase of the derived signal. The loop can be continuous or non-continuous.
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Citations
53 Claims
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1. A circuit for canceling an interference signal, the circuit comprising:
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a receive path that includes a downconverter, the downconverter to output a first signal related to the interference signal;
a canceller to output a second signal that is related to the first signal; and
a first coupler to couple the second signal into the receive path before the downconverter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method to cancel an interference signal in a RFID transceiver, the method comprising:
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downconverting a signal propagating in a receive path that includes a downconverter;
sensing the downconverted signal;
providing an adjustment signal that depends on the sensed signal; and
coupling the adjustment signal into the receive path upstream from the downconverter. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. An apparatus to cancel an interference signal in a RFID transceiver, the apparatus comprising:
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means for downconverting a signal propagating in a receive path;
means for sensing the downconverted signal;
means for providing an adjustment signal that depends on the sensed signal; and
means for coupling the adjustment signal into the receive path before downconverting. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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34. A circuit to cancel carrier signal interference in a RFID system having a downconverter used in receiving a modulated signal, the circuit comprising:
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a first coupler to output a signal derived from a carrier signal of the RFID system;
an adjustment circuit to adjust the derived signal as a function of an output signal of the downconverter; and
a second coupler to combine the adjusted signal and a signal received by a RFID reader before being downconverted by the downconverter. - View Dependent Claims (35, 36, 37, 38, 39, 40, 41, 42)
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43. A reader for use in an RFID system, the reader comprising:
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a transmit path to propagate a carrier signal of the RFID system;
a first coupler to output a signal derived from the carrier signal;
a receive path including a direct conversion receiver;
an adjustment circuit to adjust the derived signal as a function of an output signal of the direct conversion receiver; and
a second coupler to inject the adjusted signal into the receive path upstream from the direct conversion receiver. - View Dependent Claims (44, 45, 46, 47, 48, 49, 50, 51, 52, 53)
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Specification