A method and apparatus for tracking items automatically is described. A passive RFID (Radio Frequency IDentification) tag is used with a material tracking system capable of real-time pinpoint location and identification of thousands of items in production and storage areas. Passive RFID tags are attached to the item to be tracked, remote sensing antennas are placed at each remote location to be monitored, interrogators with several antenna inputs are connected to the sensing antennas to multiplex the antenna signals, and a host computer communicates with the interrogators to determine item locations to an exacting measure.

RFID material tracking method and apparatus

An RFID system and method for communicating between a host computer, one or more interrogators connected to the host computer, and a large body of transponders distributed within an area covered by the interrogators. Each transponder originally has a common identification code, and upon initialization by the host computer internally generates a unique identification code based upon an internally generated random number. The host, through the interrogators, reads each of the identification codes associated with each transponder by iteratively transmitting a read identification code command along with a controlled variable. Each transponder compares the received controlled variable to an internally generated random number, and selectively transmits its identification code based upon the outcome of this comparison. After the completion of each read identification code iteration, the host adjusts the controlled variable based upon the responses received in the previous iteration. Preferably, communications between the interrogators and the transponders are DSSS signals in TDMA format, and the transponders use the random number generator to assign a time slot for transmission of their response. Each interrogator includes an antenna system utilizing a switch matrix to connect multiple antennas having different polarizations, which ensures that all transponders within the range of the interrogator receive the signals from the interrogator. In a further aspect, the interrogators are arranged in groups, each group in nearest neighbor format, to reduce the time for reading the transponders and the emissions generated when more than one interrogator is active at the same time.

Method and system for communicating with and tracking RFID transponders

An electronic tire maintenance system is provided for measuring a parameter of a device at a first location. The system includes a sensor for measuring the device parameter and generating a data signal representing the measured parameter. The system also includes a microprocessor coupled to the sensor for activating the sensor on a first periodic basis to measure the device parameter. The microprocessor includes a memory for storing the generated data signal representing the measured parameter. A transmitter and a receiver are coupled to the microprocessor. The microprocessor periodically partially awakens to determine, on a second periodic basis, if a received transmission is a valid interrogation signal and, if so, fully awakens and responds to the valid interrogation signal, via the transmitter, by at least transmitting the last stored measured parameter. In one embodiment, the device is a tire tag mounted inside a tire that measures tire data and transmits that data to a remote source in response to an interrogation request, an alert condition, or automatically on a periodic basis.

Electronic tire management system

An interrogator, methods of discerning the presence of an object, and interrogation systems employing the same. In one embodiment, the interrogation systems include multiple interrogators that communicate with a base command unit to track a location of an object. In another embodiment wherein the object is an RFID object (e.g., an object with an RFID tag), the interrogators employ signal processing techniques such as precharging the RFID object, and correlating a reference code with a reply code from the RFID object using selected techniques to increase a sensitivity of the interrogator, especially for adverse environments. In other embodiments, the interrogation systems include variations of metal instruments and sponges employed therewith. In yet another embodiment, the interrogation system includes metal interrogators capable of discerning the presence of a metal object, especially in a presence of another metal object.

Interrogator and Interrogation System Employing the Same

An advertising compliance monitoring system is provided that includes a tag affixed to a sign or marketing material or shopper ID card, the tag communicating with a reader on a periodic basis. The tag includes a memory for storing tag data, a transmitter and a receiver. The tag uses sleep modes to conserve power. The tag transmits tag data to a reader in response to an interrogation request, or automatically on a periodic basis. The tag data includes an identification number used to identify the tag associated with a particular sign, price, marketing material or shopper, status data (e.g., delivered, displayed), and time and date information. This data is processed by a central server to determine compliance with and/or exposure to a particular advertising program.

Advertising compliance monitoring system

Communications between an RFID interrogator and an RFID transponder require that no more than one transponder be present in the reading range of the interrogator and transmitting into motion at any given time. If multiple transponders are in the field, then a collision between the return signals of the transponders occurs, rendering the signals unreadable. A method to resolve the collisions and allow for accurate transmission of each transponder's data is given. This method is especially effective over other methods when the transponder is a read-only type of device, whereby there is no communications interrogator on board the read-only transponder.

Method for resolving signal collisions between multiple RFID transponders in a field

A response-adjustable temperature sensor (306, Rext), particularly for a
transponder (102, 200, 400) capable of measuring one or more parameters
(e.g., temperature, pressure) and transmitting a data stream (Figures 3C, 4B) to
an external reader/interrogator (106). The transponder typically operates in a
passive mode, deriving its power (Vxx, Vcc, Vdd) from an RF interrogation
signal received by an antenna system (210, 410), but can also operate in a
battery-powered active mode. The transponder includes memory (238, 438) for
storing measurements, calibration data, programmable trim settings (436b),
transponder ID and the like. The temperature sensor is a temperature
measurement device characterized by a resistance (Rext, 216, 416, 716) and a
temperature sensing circuit (306) comprising a temperature sensing transistor
(Q1) which exhibits a predictable change in its base-emitter voltage due to
temperature, and transistors (P1, N1, P2, N2) connected for mirroring a current
(I(T)) through the temperature sensing transistor and through the resistance.
The resistance may be a fixed, temperature-independent resistor or a
resistance that has a resistance value that predictably varies with temperature,
such as a thermistor (716). Temperature response and resolution can be
adjusted while maintaining desired current levels by varying the value of the
resistance and also by selecting a thermistor with a suitable temperature
coefficient. User-settable trimming bits can be used to determine scaling of the
transponder output. Replacing an external pressure-sensing capacitor with a
fixed-value capacitor allows further flexibility in scaling of the output when only
temperature readings are needed.

Response adjustable temperature sensor for transponder

A pneumatic tire monitoring system for monitoring pneumatic tire conditions for one or more tire/wheel assemblies mounted on a vehicle, preferably in combination with a tire pressurizing and regulating apparatus, comprises a transponder with a transmitting antenna mounted on the wheel for transmitting a signal indicating tire condition, one or more receivers with receiving antennas fixedly mounted on the vehicle, and circuitry for processing the received signals; the system characterized in that: circuitry for each transponder is on a printed circuit board within a protective housing coaxial to the hub of the wheel or wheel carrier; and each transmitting antenna is selected from the group comprising a partial loop antenna, a helical antenna, a circular dipole antenna, and a small coupling coil adjacent to an endless hoop antenna. The partial loop antenna is mounted in each housing affixed around a portion of the circumference of the printed circuit board, having an angular arc length, and comprises a serpentine portion for increasing the effective length of the partial loop antenna without also extending the angular arc length. The angular arc length and the affixed placement are determined for avoiding RF signal interference due to interaction with signal-interfering objects in the housing. Additionally, the partial loop antenna has an end portion that can be trimmed for adjusting the effective length to enable tuning of the antenna for optimum transmission at different radio transmission frequencies.

Pneumatic tire monitor

Acquiring and collecting data from a subject animal. A system includes a passive data acquisition device associable with a subject animal including: a sensor, a radio frequency identification (RFID) transponder, and a magnet separate form the transponder. The system also includes a transceiver operable to activate the data acquisition device and to receive and demodulate an RFID telegram from the data acquisition device sent in response to the activation. The transceiver includes an activation antenna configured to encompass areas of substantially equal and substantially opposite flux and a receive antenna configured symmetrically along an axis of symmetry of the activation antenna. The RFID telegram from the data acquisition device to the transceiver comprises an ISO 11784-compliant identification code containing sensor data in the reserved field of the code. In another embodiment, the RFID telegram comprises a modified ISO 11785 telegram.

Livestock data acquisition and collection

A radio frequency (RF) transponder (200) capable of measuring parameters associated with an object and transmitting data to an external reader/interrogator (106, 400). In use with a pneumatic tire (104), the transponder measures temperature and pressure withinthe tire. The transponder includes circuitry (226) for controlling windows of time (WT and WP) during which real-time temperature and pressure measurements are made, and for storing (236) calibration data, transponder ID number and the like, and for transmitting this information in a data stream (Figure 3C) to the reader/interrogator. An excessive temperature condition may also be sensed (MTMS 218) and included in the data stream. The circuitry of the transponder is preferably implemented on a single IC chip (204), using CMOS technology, with few components external to the IC chip. The transponder is preferably passive, deriving its operating power from an RF signal provided by the exernal reader/interrogator. Data (NT) indicative of temperature and data (NP) indicative of pressure are both transmitted to the reader/interrogator, along with calibration data. A calibration data stored by the transponder and transmitted in the data stream is a slope of NT/NP, or the 'ratioed' response of the temperature count divided by the pressure count, which is determined during calibration of the transponder.

Dale Lee Yones

Papers

Method for resolving signal collisions between multiple RFID transponders in a field

Response adjustable temperature sensor for transponder

Pneumatic tire monitor

Livestock data acquisition and collection

Rf transponder and method of measuring parameters associated with a monitored object