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 present invention relates to a system for communication between a monitor and multiple transceivers. The monitor includes a resonant circuit and a transmitter, while the transceivers have a resonant circuit, a receiver, a memory, a comparator, a counter, and a transmitter. The system uses a method for communicating between the monitor and transceivers that includes transmitting a first frequency for a first duration, receiving a response signal from the transceivers, and determining a second frequency based on the response signal. This allows for better communication with the transceivers even if they are close to the monitor, and can also improve sensitivity and reliability. The system can also use phase detection or signal analysis to determine the second frequency more accurately. The identification number of each transceiver is determined by transmitting a number and repeating the process until a unique identification number is reached. The system can extend the communication range and improve the efficiency of transferring operative power to the transceivers. The method for determining the identification number includes transmitting a start signal, receiving a reply, and repeating the process until a unique identification number is reached. The system can also use a memory to store the first and second codes for comparison. The technical effects of the invention include improved communication between the monitor and transceivers, increased sensitivity and reliability, extended communication range, and reduced power consumption."

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.

Images