Patent Publication Number: US-2009218891-A1

Title: Method and apparatus for rfid based smart sensors

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/032,528, entitled “Method and Apparatus for RFID Smart Sensors,” filed on Feb. 29, 2008, currently pending. 
    
    
     BACKGROUND 
     Radio frequency identification (RFID) based sensors of the present technology can be utilized in the field of monitoring, detecting, tracking, and reporting at least one specific sensor based parameter. Such RFID sensors can be utilized in applications including, for example, electrical, chemical, biological, radiological, environmental, or intrusion sensing. 
     RFID is an automatic identification method, relying on storing and remotely retrieving data using devices called RFID tags or transponders. The technology generally utilizes an RFID reader and an RFID tag. An RFID tag can be applied to or incorporated into a product, animal, or person for the purpose of identification and tracking. Most RFID tags contain an integrated circuit for storing and processing information, as well as for modulating and demodulating a radio-frequency (RF) signal sent to or received from the reader, and an antenna for receiving and transmitting the RF signal. There are generally two types of RFID tags: active RFID tags, which contain a battery, and passive RFID tags, which have no battery. 
     RFID has been widely utilized for asset tracking or inventory controls, such as in inventory tracking for shipping and retail applications. This has historically been a passive RFID technology, where an RFID tag is powered by the energy transmitted from the reader when it sends a radio frequency (RF) transmission to the RFID tag to retrieve an embedded UPC code, serial number, or asset control number. 
     BRIEF SUMMARY 
     RFID devices can be powered by one or more sources of RF energy, including available RF energy. RFID can be utilized to measure data, or receive data transmitted to the RFID device, and can preferably store the data and transmit the data to an RFID reader or other data receiver. 
     In one aspect, an RFID device is provided that includes an energy harvesting and storing system that receives available RF energy and uses the available RF energy to power the RFID device. 
     In another aspect, an RFID device is provided that includes an energy harvesting and storing system that receives available RF energy and uses the available RF energy to power the RFID device, a microprocessor connected to the energy harvesting and storing system, a transceiver connected to the microprocessor, and a data transmission antenna connected to the transceiver. 
     In a third aspect, an RFID device is provided that includes an energy harvesting and storing system that receives available RF energy and uses the available RF energy to power the RFID device, a microprocessor connected to the energy harvesting and storing system, one or more sensors connected to the microprocessor that can measure data, a transceiver connected to the microprocessor, and a data transmission antenna connected to the transceiver. 
    
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
       Specific embodiments of the invention have been chosen for purposes of illustration and description, and are shown in the accompanying drawings, forming a part of the specification. 
         FIG. 1 . is schematic diagram of one embodiment of an energy harvesting and storing system of an RFID device. 
         FIG. 2  is a schematic diagram of one embodiment of an RFID smart sensor device. 
         FIG. 3  is a diagram of one embodiment of an RFID smart sensor device. 
     
    
    
     DETAILED DESCRIPTION 
     The RFID devices disclosed herein can be utilized to measure data, or receive data transmitted to the RFID device, and can preferably store the data and transmit the data to an RFID reader or other data receiver. In some examples, RFID devices can include one or more sensors that can measure data. In other examples, RFID devices can receive data transmitted from a remote data gathering device. In some examples, the RFID devices also include data logging capabilities, and can store data that corresponds to one or more data readings. 
     RFID devices of the present technology can be powered in any suitable manner. In at least some examples, RFID devices include an antenna that receives available RF energy, and the RFID device can thus be powered from a single source or a plurality of sources. For example, RFID devices described herein can be powered from one or more sources of available RF energy. The term “available RF energy” should be understood to encompass RF energy that is transmitted generally in the area of the RFID device, and is thus available to the RFID device, regardless of the source transmitting the RF energy, where such RF energy is not directed in a focused manner specifically to the RFID device. Conventional passive RFID technology relies upon RF energy directed from an RFID reader specifically to an RFID device. Instead, RF energy received by the present RFID devices can be collected from any available source of RF energy that is receivable by the RFID device. The RF energy received by the RFID device can thus be intercepted and collected from transmissions sent by one or more sources for purposes unrelated to powering the RFID device, including but not limited to, RF energy from commercial radio broadcasts on AM radio bands or FM radio bands, or broadcast television transmissions. In other examples, one or more dedicated transmitters can be utilized in an area that is local to the sensor, such as being within a radius of a few miles, or a smaller radius, such as for example, a radius of a few hundred feet, and can transmit RF energy that can be received by one or more RFID devices. Such dedicated transmitters can be licensed or un-licensed, and can operate on non-commercial bands. The dedicated transmitters can broadcast RF energy within the intended radius, and one or more RFID devices can receive the RF energy. The RF energy received by the RFID device can power the device to perform tasks of monitoring and reporting information from various types of sensors. 
       FIG. 1  illustrates an energy harvesting and storing system  100  that can be utilized in an RFID device. The energy harvesting and storing system  100  can receive available RF energy and use the available RF energy to power the RFID device. The system  100  can utilize ultra low power techniques to gather and store power derived from the available RF energy. The system  100  includes an RF receiving antenna  102  that receives RF energy, preferably available RF energy from one or more RF energy sources. The system  100  also includes at least one transistor  104 , which forms a broadband tuner circuit with the RF receiving antenna  102 . The at least one transistor  104  can preferably operate at voltage levels down to less than about 0.6 volts, including, for example, about 0.1 volts. RF energy collected by RF receiving antenna  102  can be provided to a diode  106  that converts the received RF energy to a DC voltage. The DC voltage as converted from the received RF energy can tend to be a low voltage, and can be in the range of from about 0.1 volts or greater. The DC voltage from the diode  106  can be boosted to a value high enough to run the RFID device using voltage doubling or tripling circuitry. For example, the DC voltage from the diode  106  can be provided to a charge pump  108 , which can convert DC voltage to a higher DC voltage. In one example, the DC voltage can be increased by the charge pump  108  to a voltage of about 5 volts. The DC voltage produced by the charge pump  108  can be provided to a capacitor  110 . Capacitor  110  can be a super capacitor that removes the ripple from the DC voltage as received from the charge pump and stores the DC voltage for use in powering the RFID device. In an alternative embodiment, capacitor  110  can be a low voltage capacitor that removes the ripple from the DC voltage as received from the charge pump, and the DC voltage can be stored in a super capacitor located elsewhere in the system. The system  100  can also include a transistor  112  and a regulator  114 . The system  100  can provide a regulated DC voltage V out  that can power the RFID device. 
       FIG. 2  illustrates an RFID device  200  that includes an energy harvesting and storing system. The energy harvesting and storing system can preferably store enough energy in at least one super capacitor  202  to allow a microprocessor  204  and at least one sensor  206  to activate periodically, take a measurement, store the value of the measurement, and later provide the stored data to a data receiver. As illustrated, RF energy  208  can be received by an RF receiving antenna  210 . The RF energy can be received from at least one source of RF energy, and can be received from a plurality of sources of available RF energy. The received RF energy can be provided to one or more transistors  212 . The received RF energy can be provided to a diode  214  that converts the received RF energy to a DC voltage. In some embodiments, as described with reference to  FIG. 1  above, the DC voltage from the diode  106  can be boosted to a value high enough to run the RFID device using voltage doubling or tripling circuitry. The DC voltage can then be provided to and stored by the super capacitor  202 . 
     As further illustrated in  FIG. 2 , the super capacitor  202  can provide power to the other components of the RFID device, which can include a microprocessor  204 , at least one sensor  206 , a transceiver  216 , and a data transmission antenna  218 . In at least one example, power from the super capacitor  202  can be utilized to periodically activate the at least one sensor  206 . When activated, the at least one sensor  206  can measure data and provide the measured data to the microprocessor  204 . The microprocessor  204  can utilize power received from the super capacitor  202  to perform any of a number of functions, including, but not limited to, converting the data from the at least one sensor  206  to a digital representation, storing the data, and transmitting the data through the transceiver  216  and the data transmission antenna  218 . The data transmission antenna  218  transmit data from the RFID device to an RFID reader or other data receiver. Such transmissions can occur periodically, or upon receipt of a query or commend from the RFID reader or other data receiver. 
       FIG. 3  illustrates an RFID device  300 . The RFID device  300  includes a housing  302 , an energy harvesting and storing system  304 , a microprocessor  306 , a sensor  308 , a transceiver  312 , and a data transmission antenna  314 . The sensor  308  can measure data via one or more sensor portals  310  in the housing  302  of the RFID device  300 . 
     RFID devices of the present technology may be used in the fields of monitoring, detecting, tracking, and reporting a specific sensor based parameter in the areas of electrical, chemical, biological, radiological, environmental, or intrusion sensing. Examples of these can range from chemical sensors useful in detecting the change in products that have a specific shelf life, to bio-sensors useful in monitoring biologically active products, to radiological sensors useful in detecting high radiation levels, to seismic sensors useful in detecting seismic activity, to implantable devices useful in monitoring blood sugar levels or other blood borne antigens, as well as to numerous other applications. 
     In one application, an RFID sensor device can be utilized for monitoring blood sugar levels. A rechargeable wrist reader can be utilized to provide RF energy to the body implantable RFID smart sensor device. The sensor in the RFID smart sensor device can activate periodically, such as every few hours or at other time intervals, to measure and store data relating to the blood sugar level of a patient. The RFID smart sensor device can be issued a command via RF from the wrist reader or from another command device, and can transmit the stored data to the wrist reader or other command device regarding the blood sugar levels of the patient. 
     In another application, an RFID sensor device can be utilized as a shelf life monitoring device. The RFID sensor device can be placed upon a shelf that contains perishable food items. The sensor in the RFID sensor device can activate periodically, such as daily or at other time intervals, to measure and store data relating to the status of the food items. 
     In a third application, an RFID device can receive and store transmitted data from a remote data measuring device, and can later transmit the stored data to a data receiving device. For example, livestock tagged with an RFID device can be weighed, and the weight data for each animal can be transmitted to, received by, and stored on the RFID device worn by the animal. The data can be stored over a period of time, and then can be transmitted to a data receiver to monitor and track the weight or health of the animal. 
     From the foregoing, it will be appreciated that although specific examples have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit or scope of this disclosure. It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to particularly point out and distinctly claim the claimed subject matter.