Battery assisted RFID tag with square-law receiver and optional part time active behavior
First Claim
1. A method for operating a battery assisted tag within an RFID system, the method comprising:
- monitoring at least one characteristic of a detected RF signal at a receiver within the battery assisted tag;
in response to determining the at least one characteristic satisfies a first criteria, operating the battery assisted tag within a first dynamic range state during which battery power is provided to circuitry within the battery assisted tag; and
in response to the at least one characteristic satisfying a second criteria, operating the battery assisted tag within a second dynamic range state during which the battery assisted tag functions in a square law mode, andwherein the at least one characteristic comprises one or more of a power level of the detected RF signal and a signal-to-noise ratio of the detected RF signal.
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Accused Products
Abstract
Embodiments of the present invention provide RFID systems having battery-assisted, Semi-Passive RFID tags that operate with sensitive transistor based square law tag receivers utilizing a plurality of tag receiver dynamic range states. Embodiments of the present invention are also enhanced with receiver training and synchronizing methods suited to the high tag sensitivity and need for dynamic range state switching. These enhancements may employ pseudo-random sequence based receiver training, activation signaling, and frame synchronizing. Further enhancement is achieved via design of system command sets and tag state machine behavior that control system interference and allow maximum usage of high sensitivity. Command set design also allows for convenient expansion to active transmitters and receivers in tags operating within the same system. Additional enhancement attained via power leveling methods that optimize the amount of transmitted power and interference from a reader in relation to the sensitivity of the RFID tags, their ranges from the reader, and the unique physics of the backscatter RFID radio link.
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Citations
40 Claims
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1. A method for operating a battery assisted tag within an RFID system, the method comprising:
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monitoring at least one characteristic of a detected RF signal at a receiver within the battery assisted tag; in response to determining the at least one characteristic satisfies a first criteria, operating the battery assisted tag within a first dynamic range state during which battery power is provided to circuitry within the battery assisted tag; and in response to the at least one characteristic satisfying a second criteria, operating the battery assisted tag within a second dynamic range state during which the battery assisted tag functions in a square law mode, and wherein the at least one characteristic comprises one or more of a power level of the detected RF signal and a signal-to-noise ratio of the detected RF signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. A battery assisted RFID tag comprising a transistor-based detector, the transistor-based detector comprising:
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a bipolar transistor coupled to harvest current from an input RF signal; an impedance up-conversion circuit coupled to a base of the bipolar transistor; a compression circuit coupled to a collector of the bipolar transistor; a current mirror coupled to the compression circuit; a load coupled to a collector of the current mirror; and an integrator control system coupled to the load. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33)
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34. A battery assisted RFID tag comprising:
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a receiver coupled to receive input signal from an RFID reader, the receiver comprising; a biased transistor detector coupled to harvest a detected current from the input signal; a mirror coupled to receive the harvested current and apply a gain to the harvested current; and a negative feedback control system coupled to an output of the biased transistor detector; and an adjustable front end RF filter coupled to receive the input signal. - View Dependent Claims (35, 36, 37, 38, 39, 40)
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Specification