Active RF tag with wake-up circuit to prolong battery life
First Claim
1. An active RF transponder including electronic circuitry, comprising:
- a battery;
an antenna adapted to receive RF signals from an interrogator;
an oscillator adapted to provide a clock signal having a duty cycle; and
a wake-up circuit coupled to the antenna and the oscillator and adapted to periodically sample said RF signals for presence of an interrogation signal, said duty cycle defining the intervals during which the antenna is sampled for presence of the interrogation signal.
3 Assignments
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Accused Products
Abstract
An active RF transponder is provided with a wake-up circuit that wakes the RF transponder from a sleep state upon detection of an RF interrogating signal. The active RF transponder includes a battery, an antenna adapted to receive RF signals from an interrogator, and electronic circuitry providing the various RF transponder functions of sending/receiving signals and storing data. A first embodiment of the invention includes a wake-up circuit that periodically checks for the presence of an RF signal at the antenna. The wake-up circuit is coupled to the antenna and includes a switch adapted to selectively couple the battery to the electronic circuitry and provide electrical power thereto upon detection of the RF signals by the antenna. The wake-up circuit further comprises an oscillator providing a clock signal having a low duty cycle that defines intervals during which the antenna is sampled for presence of the RF signals (e.g., approximately 20 ns every 100 μs). A second embodiment of the RF transponder includes a wake-up circuit as in the first embodiment that is further adapted to detect a code sequence modulated in the RF signals. The code sequence is unique for a class of RF transponder, so the wake-up circuit can discriminate between interrogating signals. A third embodiment of the RF transponder includes a wake-up circuit that wakes the RF transponder upon detection of an RF signal that contains data within a desired band of frequencies. This embodiment enables the RF transponder to discriminate between RF signals that likely contain valid data and other RF noise. After the RF transponder has been waked, the wake-up circuit returns the RF transponder to a sleep state if valid data is not detected within a predetermined period of time.
319 Citations
28 Claims
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1. An active RF transponder including electronic circuitry, comprising:
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a battery;
an antenna adapted to receive RF signals from an interrogator;
an oscillator adapted to provide a clock signal having a duty cycle; and
a wake-up circuit coupled to the antenna and the oscillator and adapted to periodically sample said RF signals for presence of an interrogation signal, said duty cycle defining the intervals during which the antenna is sampled for presence of the interrogation signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An active RF transponder including electronic circuitry, comprising:
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a battery;
an antenna adapted to an receive RF signal from an interrogator;
an oscillator adapted to produce a clock signal having a duty cycle;
an analog-to-digital circuit adapted to recover digital data signals from said received RF signal; and
a wake-up circuit coupled to the analog-to-digital circuit and the oscillator and adapted to determine the frequency range of said digital data signals at intervals defined by said -duty cycle, said wake-up circuit further including a switch adapted to selectively couple the battery to the electronic circuitry and provide electrical power thereto upon detection that the digital data signals are within a predetermined frequency range. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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Specification