Synthetic aperture RFID handheld with tag location capability
First Claim
1. A radio frequency identification (RFID) reader comprising:
- a location or movement determination component comprising a sensor, the location or movement determination component configured to measure location or acceleration of the RFID reader; and
an RFID radio comprising a first antenna that transmits a first radio frequency (RF) query;
wherein a first phase and a second phase for a tag signal sent by a tag is calculated in response to the first RF query and in response to the RFID reader being moved, the first phase corresponding to the tag signal received at a first position of the first antenna, and the second phase corresponding to the tag signal received at a second position of the first antenna;
wherein a trajectory or positions of the moving reader is calculated using data from the location or movement determination component;
wherein a bearing for the tag is determined using the calculated trajectory or positions and the calculated first phase and second phase for the tag,wherein whether to take more tag signal readings is determined based on whether a minimum level of confidence has been reached, andwherein the RFID radio transmits on a different frequency when the minimum level of confidence is not achieved within a predetermined time period.
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Abstract
A system for determining a bearing or location of a radio frequency identification (RFID) tag using a handheld RFID reader is described. In one embodiment, the reader is equipped with an accelerometer. A user moves the reader while the reader receives the tag'"'"'s signal and determines the tag signal'"'"'s phase at multiple locations. The locations of the reader antenna can be reconstructed using the accelerometer data. By using the phase determined at multiple locations in conjunction with the location of the reader antenna, the reader can determine the bearing of the tag. For an RFID reader not equipped with an accelerometer, the sign and ratio of the rate of change in the phase of a tag'"'"'s signal to the distance traveled by the reader antenna can be used to determine the location of the tag relative to the reader.
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Citations
17 Claims
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1. A radio frequency identification (RFID) reader comprising:
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a location or movement determination component comprising a sensor, the location or movement determination component configured to measure location or acceleration of the RFID reader; and an RFID radio comprising a first antenna that transmits a first radio frequency (RF) query; wherein a first phase and a second phase for a tag signal sent by a tag is calculated in response to the first RF query and in response to the RFID reader being moved, the first phase corresponding to the tag signal received at a first position of the first antenna, and the second phase corresponding to the tag signal received at a second position of the first antenna; wherein a trajectory or positions of the moving reader is calculated using data from the location or movement determination component; wherein a bearing for the tag is determined using the calculated trajectory or positions and the calculated first phase and second phase for the tag, wherein whether to take more tag signal readings is determined based on whether a minimum level of confidence has been reached, and wherein the RFID radio transmits on a different frequency when the minimum level of confidence is not achieved within a predetermined time period. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A radio frequency identification (RFID) reader comprising:
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a RFID radio comprising a first antenna that is configured to transmit a first radio frequency (RF) query using the RFID radio; and wherein a processor is configured to calculate a first phase and a second phase for a tag signal sent by a tag in response to the first RF query and in response to moving the RFID reader in a first direction, wherein a first phase corresponds to the tag signal received at a first position of the first antenna, and wherein the second phase corresponds to the tag signal received at a second position of the first antenna, and wherein the first and second positions correspond to movement of the reader in the first direction, wherein a change of phase of the tag signal is calculated as a function of time using the first phase and the second phase, and wherein a location of the tag relative to the movement direction of the reader is determined based on the calculated change of phase as a function of time, wherein whether to take more tag signal readings is determined based on whether a minimum level of confidence has been reached, and wherein the RFID radio transmits on a different frequency when the minimum level of confidence is not achieved within a predetermined time period. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A method of determining a location of a radio frequency identification (RFID) tag relative to an RFID reader, the method comprising:
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providing an RFID transceiver comprising an antenna configured to send a first RF query; calculating, by a processor, a first phase and a second phase for a tag signal sent by a tag in response to the first RF query and in response to the reader moving in a first direction, wherein a first phase corresponds to the tag signal received at a first location of the first antenna, wherein the second phase corresponds to the tag signal received at a second location of the first antenna, and wherein the first and second locations correspond to movement of the reader in the first direction; calculating a change of phase of the tag signal as a function of distance traveled by the reader using the first phase and the second phase; determining a position of the tag relative to the movement direction of the reader based on the calculated change of phase as a function of time; determining a confidence level of the relative location of the tag, and if a minimum level of confidence is not satisfied, sending a second RF query using the RFID radio; and outputting the position of the tag relative. - View Dependent Claims (16, 17)
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Specification