Clock synchronization in an RFID equipped device
First Claim
1. A method for clock synchronization in a radio frequency identification (RFID) equipped device, the method comprising:
- measuring a difference between a field clock frequency generated from an external clock and an internal clock frequency generated from an internal clock; and
generating outgoing bits in the RFID equipped device in response to the measured difference, wherein generating the outgoing bits comprises adjusting the bit length of at least one of the outgoing bits in response to the measured difference while keeping an average bit length error of the outgoing bits below a predefined percentage threshold, wherein adjusting the bit length of at least one of the outgoing bits comprises adding a clock period to a non-shifting signal section of at least one of the outgoing bits or removing a clock period from a non-shifting signal section of at least one of the outgoing bits.
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Accused Products
Abstract
Embodiments of a method for clock synchronization in a radio frequency identification (RFID) equipped device, an RFID equipped device, and a hand-held communications device are described. In one embodiment, a method for clock synchronization in an RFID equipped device involves measuring a difference between a field clock frequency generated from an external clock and an internal clock frequency generated from an internal clock and generating outgoing bits in the RFID equipped device in response to the measured difference. Generating the outgoing bits involves adjusting the bit length of at least one of the outgoing bits in response to the measured difference. Other embodiments are also described.
11 Citations
18 Claims
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1. A method for clock synchronization in a radio frequency identification (RFID) equipped device, the method comprising:
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measuring a difference between a field clock frequency generated from an external clock and an internal clock frequency generated from an internal clock; and generating outgoing bits in the RFID equipped device in response to the measured difference, wherein generating the outgoing bits comprises adjusting the bit length of at least one of the outgoing bits in response to the measured difference while keeping an average bit length error of the outgoing bits below a predefined percentage threshold, wherein adjusting the bit length of at least one of the outgoing bits comprises adding a clock period to a non-shifting signal section of at least one of the outgoing bits or removing a clock period from a non-shifting signal section of at least one of the outgoing bits. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 17, 18)
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9. A radio frequency identification (RFID) equipped device comprising:
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a clock difference measurement unit configured to measure a difference between a field clock frequency generated from an external clock and an internal clock frequency generated from an internal clock; and a modulator configured to generate outgoing bits in response to the measured difference, wherein the modulator comprises a bit length adjustment unit configured to adjust the bit length of at least one of the outgoing bits in response to the measured difference while keeping an average bit length error of the outgoing bits below a predefined percentage threshold, wherein the bit length adjustment unit is configured to add a clock period to a non-shifting signal section of at least one of the outgoing bits or to remove a clock period from a non-shifting signal section of at least one of the outgoing bits. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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16. A hand-held communications device comprising:
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a crystal oscillator configured to provide an internal clock signal; and a Near Field Communication (NFC) module comprising; an antenna configured to receive NFC wireless signals; a clock difference measurement unit configured to derive an external field clock frequency from the received NFC wireless signals and to measure a difference between the external field clock frequency and an internal clock frequency of the internal clock signal; and a modulator configured to generate outgoing bits in response to the measured difference, wherein the modulator comprises a bit length adjustment unit configured to add a clock period to a non-shifting signal section of one of the outgoing bits or to remove a clock period from a non-shifting signal section of one of the outgoing bits in response to the measured difference while keeping an average bit length error of the outgoing bits below a predefined percentage threshold.
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Specification