Power conserving active RFID label

Methods and apparatus, including computer program products, for a power conserving active RFID label. A system for performing radio frequency (RF) communications includes a radio frequency identification (RFID) tag attached to one or more items to be tracked, the RFID tag configured to receive a request and a time interval indicating a time for determining a temperature and a battery voltage, and to adjust the time interval at a time of determining the temperature and the battery voltage if the detected voltage is less than a predetermined voltage, and an interrogator communicatively coupled to one or more antennas to transmit one or more requests to the RFID tag and to receive one or more responses, at least one response including a time, temperature and battery voltage.

BACKGROUND

The present invention relates to radio frequency identification (RFID), and more particularly to a power conserving active RFID label.

RFID is a technology that incorporates the use of electromagnetic or electrostatic coupling in the radio frequency (RF) portion of the electromagnetic spectrum to uniquely identify an object, animal, or person. With RFID, the electromagnetic or electrostatic coupling in the RF (radio frequency) portion of the electromagnetic spectrum is used to transmit signals. A typical RFID system includes an antenna and a transceiver, which reads the radio frequency and transfers the information to a processing device (reader) and a transponder, or RF label, which contains the RF circuitry and information to be transmitted. The antenna enables the integrated circuit to transmit its information to the reader that converts the radio waves reflected back from the RFID label into digital information that can then be passed on to computers that can analyze the data.

SUMMARY

The present invention provides methods and apparatus, including computer program products, for a power conserving active RFID label.

In one aspect, the invention features a radio frequency identification (RFID) tag including a substrate, an antenna on the substrate, and an integrated circuit operably coupled to a temperature sensor and to the antenna to receive a time interval from a RFID interrogator, the time interval indicating a time for determining a temperature and a battery voltage, the integrated circuit configured to adjust the time interval at a time of determining the temperature and the battery voltage if the detected voltage is less than a predetermined voltage.

In another aspect, the invention features a radio frequency identification (RFID) interrogator including one or more antennas, a receiver communicatively coupled to at least one of the one or more antennas to receive a response from a radio frequency identification (RFID) tag, the response including time, temperature and battery voltage, a transmitter communicatively coupled to at least one of the one or more antennas to transmit requests, and a control unit communicatively coupled to the transmitter and the receiver, wherein the receiver is configured to receive the response and adjust a time interval in the RFID tag for determining a temperature and a battery voltage if the battery voltage in the response is less than a predetermined voltage.

In another aspect, the invention features a system for performing radio frequency (RF) communications, the system including a radio frequency identification (RFID) tag attached to one or more items to be tracked, the RFID tag configured to receive a request and a time interval indicating a time for determining a temperature and a battery voltage, and to adjust the time interval at a time of determining the temperature and the battery voltage if the detected voltage is less than a predetermined voltage, and an interrogator communicatively coupled to one or more antennas to transmit one or more requests to the RFID tag and to receive one or more responses, at least one response including a time, temperature and battery voltage.

DETAILED DESCRIPTION

Radio frequency identification (RFID) labels can be intelligent or just respond with a simple identification (ID) to radio frequency (RF) interrogations. The RFID label can contain memory. This memory can be loaded with data either via an interrogator, or directly by some integrated data gathering element of the RFID label, for example, an environmental sensor. This data is retrieved some time later.

As shown inFIG. 1, an exemplary active RFID label10includes an antenna12, a transceiver14, a microcontroller16, a temperature sensor20and a battery22. Microcontroller16includes several elements including a memory18. Memory18can include a power conservation process100, fully described below. Temperature sensor20senses and transmits temperature data to memory18at intervals of time. When triggered by RF interrogation via transceiver14, microcontroller16fetches the data (i.e., time stamp and temperature) and sends it out to an interrogator as multiplexed data packets from transceiver14. In this manner, a historical temperature log stored in memory18in the active RFID label10can be retrieved. Temperature logging is limited by the size of memory18and/or life of battery22.

In some examples, RFID label10stores a voltage of its battery22along with a time and a temperature at each time interval.

As shown inFIG. 2, an exemplary RFID interrogator50includes an antenna52, transceiver54, memory56, central processing unit (CPU)58and optional user interface (UI)60. The RFID interrogator50performs Time Division Multiplexing (TDM) with the transceiver54and antenna52. Data (e.g., time, temperature and/or battery voltage) downloaded from the RFID label10can be stored in memory56.

The RFID interrogator50can be used to program the active RFID label10to record or log a temperature and/or battery voltage in memory18with a time interval starting at an initial time. At each time interval, e.g., every hour, the active RFID label10records a time, temperature and/or battery voltage in memory18. The RFID interrogator50can download the time, temperature and/or battery voltage data from memory18to memory56.

Over a period of service, i.e., the recording and storing of time/temperature/voltage, the life of the RFID label battery22in the active RFID label10can diminish and eventually fail. In one example, if the active RFID label10detects reduced voltage in the battery22, the active RFID label10can increase the time interval for temperature and/or voltage readings, thus conserving the remaining life of the battery22. For example, if the initial time interval in the active RFID label10is sixty minutes, the active RFID label10will log a time, temperature and/or voltage every sixty minutes. If the active RFID label10detects a voltage in the battery is less than 80% capacity, for example, the active RFID label10will increase the time interval for readings to, for example, one hundred twenty minutes. At subsequent readings, the active RFID label10will increase the time interval for readings as the battery22continues to deteriorate, i.e., as a voltage in the battery22decreases with each reading, and the active RFID label10can continue to increase the time interval for temperature and/or voltage readings, thus extending the remaining life of the battery22.

In another example, stored data received from the RFID label10can be analyzed by the RFID interrogator50. More specifically, from stored voltage data, the RFID interrogator50can determine whether the most recent voltage of the battery22is too low, or has dropped below a selected value, or that the voltage of the battery22is decreasing at too rapid a rate. In any event, the RFID interrogator50can instruct the RFID label10to increase its time interval of temperature and/or voltage readings or the RFID interrogator50can adjust its frequency of interrogations of RFID label10.

In another example, the RFID label10does not store any time, temperature and/or voltage data. Instead, during each interrogation of RFID label10, the RFID interrogator50requests the RFID label10for a current battery voltage and/or temperature. The RFID interrogator50can store temperatures and/or voltages over time. In addition, the RFID interrogator50can determine to increase its time interval between interrogators based on the currently polled battery voltage.

As shown inFIG. 3, the power conservation process100includes receiving (102) an initial time interval. Process100determines (104) whether the time interval is reached. If the time interval is reached, process100detects (106) a time from its internal clock, a temperature from its temperature sensor and voltage of its power supply, e.g., battery.

Process100determines (108) whether the detected voltage has reached a selected reduced level. If the detected voltage has not reached a selected reduced level, process100stores (110) the detected time and temperature.

If the detected voltage reached the selected reduced level (or less), process100increases (112) the time interval and stores (110) the detected time and temperature.

Process100then determines (104) whether the increased time interval is reached.

Process100can be incorporated into the memories of other types of RFID labels. For example, process100can be used with beacon tags. In general, a beacon tag is an active RF tag that can be factory set to transmit a periodic RF signal used for location, process and presence detection and tracking. Typically, these devices are placed into non-metallic enclosures and transmit an RF signal to an RFID reader located at a distance of3-10meters. As the power decreases, process100can increase the time at which the period RF signal is transmitted.

In another embodiment, memory56contains a time interval process200. As shown onFIG. 4, the time interval process200includes sending (202) an interrogation signal to a RFID label. Process200receives (204) a response signal from the RFID label containing the label's log of times, temperatures and voltages.

Process200determines (206) whether the most recent measured voltage of the label battery is below a minimum voltage. If the most recent voltage of the label is below a minimum, process200sends (208) a signal to the RFID label lengthening its time interval.

Process200determines (210) whether the rate of voltage decrease of the label battery exceeds a specified rate. The rate of decrease in battery voltage is determined by the RFID interrogator from the received store of battery voltages received from the RFID label during the interrogation. If the rate of decrease of battery voltage exceeds the specified rate, process200sends (208) a signal to the RFID label lengthening its time interval.

In another embodiment, memory56contains a polling interval process300. As shown inFIG. 5, the polling interval process300includes sending (302) an interrogation signal to a RFID label. Process300receives (304) a response signal from the RFID label containing the current battery voltage in the RFID label.

Process300determines (306) whether the current battery voltage in the RFID label is below a specified minimum. If the current battery voltage is below the specified minimum, process300lengthens (308) a time to sending its next interrogation signal.