RFID tag and RFID system having the same
First Claim
1. A radio frequency identification (RFID) tag comprising:
- a tag antenna which receives an input power from an RFID reader and radiates a reflection power corresponding to the input power to the RFID reader; and
a tag driver which is electrically connected to the tag antenna, modulates a carrier wave corresponding to the input power, provides the modulated carrier wave and the reflection power to the tag antenna, and adjusts a capacitance according to the intensity of the modulated carrier wave for impedance matching with the tag antenna,wherein the tag driver comprises;
an accumulation mode capacitor, the capacitance is changed if the reflection power is higher than a minimum power for backscattering, which modulates the carrier wave and loads the signal wave including the data into the carrier wave, and the minimum power is calculated as below;
where Pbs is the minimum power for backscattering, Pa is an effective power which is transmitted from the tag antenna and input to the tag driver, ρ
1 is a reflection coefficient if a digital signal value of the signal wave is 0, and ρ
2 is a reflection coefficient when the digital signal value of the signal wave is 1.
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Accused Products
Abstract
An RFID tag capable of enhancing the reliability of products and an RFID system having the same are provided. The RFID tag includes a tag antenna receiving waves from an RFID reader, and a tag driver. The tag driver includes an accumulation mode capacitor adjusting a capacitance value corresponding to an input voltage. That is, the tag driver adjusts the amplitude of a modulated carrier wave using the accumulation mode capacitor. Accordingly, the RFID tag adjusts the impedance of the tag driver without adjusting the current transmitted from the tag driver. Therefore, impedance adjustment of the tag driver can prevent the voltage transmitted from the tag driver from being lower than the reference voltage, and modulation and demodulation can be stably performed. As a result, the reliability of products can be enhanced.
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Citations
8 Claims
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1. A radio frequency identification (RFID) tag comprising:
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a tag antenna which receives an input power from an RFID reader and radiates a reflection power corresponding to the input power to the RFID reader; and a tag driver which is electrically connected to the tag antenna, modulates a carrier wave corresponding to the input power, provides the modulated carrier wave and the reflection power to the tag antenna, and adjusts a capacitance according to the intensity of the modulated carrier wave for impedance matching with the tag antenna, wherein the tag driver comprises; an accumulation mode capacitor, the capacitance is changed if the reflection power is higher than a minimum power for backscattering, which modulates the carrier wave and loads the signal wave including the data into the carrier wave, and the minimum power is calculated as below; where Pbs is the minimum power for backscattering, Pa is an effective power which is transmitted from the tag antenna and input to the tag driver, ρ
1 is a reflection coefficient if a digital signal value of the signal wave is 0, and ρ
2 is a reflection coefficient when the digital signal value of the signal wave is 1.- View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A radio frequency identification (RFID) system comprising:
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an RFID reader which radiates an input power; and an RFID tag comprising a tag antenna which receives the input power from the RFID reader and radiates a reflection power including a carrier wave to the RFID reader, and a tag driver which is electrically connected to the tag antenna, wherein the tag driver comprises; a memory which stores data; a controller which detects the data from the memory corresponding to the input power, modulates the carrier wave, and generates the reflection power with the carrier wave modulated corresponding to the input power; and an accumulation mode capacitor which adjusts an impedance of the tag driver by adaptively adjusting the capacitance according to the intensity of a voltage of the reflection power, and receives the reflection power from the controller and provides the reflection power to the tag antenna, the capacitance of the accumulation mode capacitor being changed if the reflection power is higher than a minimum power for backscattering, which modulates the carrier wave and loads the signal wave including the data into the carrier wave, and the minimum power is calculated as below; where Pbs is the minimum power for backscattering, Pa is an effective power which is transmitted from the tag antenna and input to the tag driver, ρ
1 is a reflection coefficient if a digital signal value of the signal wave is 0, and ρ
2 is a reflection coefficient when the digital signal value of the signal wave is 1.
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Specification