NOISE CANCELLATION FOR RFID BACKSCATTER
First Claim
1. An interrogator comprising:
- at least one antenna;
a coupler, the coupler including;
a first I/O port receiving a transmit signal;
a second I/O port outputting the transmit signal and receiving a receive signal from the at least one antenna;
a third I/O port outputting a first signal electrically coupled to the transmit signal and receiving a canceling signal;
a fourth I/O port outputting a resultant signal, the resultant signal being a combination of the canceling signal and a second signal, the second signal electrically coupled to the receive signal.
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Accused Products
Abstract
Methods and apparatuses for removing unwanted noise by a radio frequency identification (RFID) interrogator are provided. The interrogator transmits a transmitted signal while receiving a received signal. The received signal can include backscatter modulated signals from one or more RFID tags, as well as unmodulated reflections of the transmitted signal from the environment. The unmodulated reflections are undesirable and may make tag signal extraction difficult. A canceling signal is summed with the received signal to cancel or reduce the unmodulated reflections prior to tag signal extraction. In a specific embodiment, a phase shifted, amplitude adjusted reflection of the transmit signal is used by a directional coupler as the canceling signal.
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Citations
25 Claims
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1. An interrogator comprising:
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at least one antenna; a coupler, the coupler including; a first I/O port receiving a transmit signal; a second I/O port outputting the transmit signal and receiving a receive signal from the at least one antenna; a third I/O port outputting a first signal electrically coupled to the transmit signal and receiving a canceling signal; a fourth I/O port outputting a resultant signal, the resultant signal being a combination of the canceling signal and a second signal, the second signal electrically coupled to the receive signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A monostatic interrogator comprising:
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at least one circularly polarized antenna; a signal generator; a coupler, the coupler including; a first I/O port receiving a transmit signal from the signal generator; a second I/O port outputting the transmit signal and receiving a receive signal from the at least one circularly polarized antenna; a third I/O port outputting a first signal electrically coupled to the transmit signal, the third I/O port receiving a canceling signal from a reflection circuit; a fourth I/O port outputting a resultant signal, the resultant signal being a combination of the canceling signal and a second signal, the second signal electrically coupled to the receive signal. - View Dependent Claims (16, 17, 18, 19)
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20. A method comprising:
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transmitting a continuous wave transmit signal; receiving a receive signal, the receive signal including a backscattered modulated tag signal; providing a canceling signal, the canceling signal being an attenuated and phase shifted transmit signal; and combining, by a directional coupler, the receive signal with the canceling signal. - View Dependent Claims (21, 22, 23, 24, 25)
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Specification