Radio frequency identification device

Abstract

A radio frequency identification device includes a transceiver having a resonant circuit, a rectifier, a charge pump, a state machine, and a transmitter. The resonant circuit includes an antenna and has a resonant frequency. The rectifier is coupled to the resonant circuit to provide a rectified signal in response to energy from the antenna. The charge pump is enabled in response to the rectified signal to provide a first logic signal. The state machine provides a second logic signal in response to the first logic signal. The transmitter includes an amplifier coupled to the resonant circuit to form a Colpitts oscillator that is enabled by the second logic signal to transmit a response signal for identifying the radio frequency identification device.

Description

FIELD OF THE INVENTION Embodiments of the present invention relate to communication systems of the type having multiple transmitting and receiving devices that share a common communication medium; and, to methods for establishing communication in the presence of large numbers of such devices. BACKGROUND OF THE INVENTION Conventional data communication systems have been applied to accomplish object identification using the medium of radio broadcast. Such radio frequency identification (RFID) systems find application in the fields of materials handling, inventory control, and generally in the field of tracking personnel, objects, and animals. In an exemplary arrangement, such a system may include an interrogator and several thousand transceivers, each transceiver being packaged as a disposable label or tag and placed on an object, animal, or person to be tracked. Each transceiver is manufactured using integrated circuit technology, programmed with a unique identifier, and assembled ...

AI Technical Summary

Benefits of technology

The monitor may further include a first antenna coupled to the first transmitter and a squelch circuit for dissipating energy on the antenna after lapse of the first duration and before receiving from the first receiver the response signal from the resonant circuit. By quickly dissipating energy, the response signal may be more quickly and accurately received by the second receiver and consequently the second frequency may be more quickly and accurately determined, increasing system sensitivity and reliability. Obtaining quicker receiving from the second receiver extends the operating range of the monitor or permits operation with weaker signals. Weaker signals may originate from transceivers located further from the monitor or in an orientation that is detrimental to reception by the first receiver. Such detrimental orientation of the antenna in the transceiver may be with respect to the first antenna of the monitor or with respect to other transceivers proximate to the transceiver antenna.

A carrier in one implementation according to various aspects of the present invention includes an antenna and a series capacitor for tuning the antenna. Enhanced transceiver communication results when transceivers are placed in the carrier. In an alternate implementation, a carrier includes a first and a second antenna each with a respective tuning capacitor. The first and the second antenna are coupled to cooperate. Energy received in a first pattern is re-radiated in second pattern for further enhanced transceiver communication.

Problems solved by technology

Transceivers of the type having a resonant circuit coupled to an antenna, when operating in close proximity to each other, may interfere with the response from a single transceiver by absorbing the energy intended to be received by the transceiver, absorbing the energy transmitted by the transceiver, or altering the resonant frequency of the resonant circuit.

Weaker signals may originate from transceivers located further from the monitor or in an orientation that is detrimental to reception by the first receiver.

Such detrimental orientation of the antenna in the transceiver may be with respect to the first antenna of the monitor or with respect to other transceivers proximate to the transceiver antenna.

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