Non-limiting and non-exhaustive embodiments are described with reference to the following drawings, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified. The sizes and relative positions of elements in the drawings are not necessarily drawn to scale. For example, the shapes of various elements and angles are not drawn to scale, and some of these elements are arbitrarily enlarged and positioned to improve drawing legibility. Further, the particular shapes of the elements as drawn, are not intended to convey any information regarding the actual shape of the particular elements, and have been solely selected for ease of recognition in the drawings.
Embodiments of techniques to provide power to an RFID tag using a microstructure power device are described herein. In the following description, numerous specific details are given to provide a thorough understanding of embodiments. One skilled in the relevant art will recognize, however, that the embodiments can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations associated with RFID tags and RFID readers, computer and/or telecommunications networks, and/or computing systems are not shown or described in detail to avoid obscuring aspects of the embodiments.
Unless the context requires otherwise, throughout the specification and claims which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense, that is as “including, but not limited to.”
Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
The headings provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.
As an overview, one embodiment provides power to wireless data carrier, such as an RFID tag, using a microstructure power device that is capable of supplying microwatts of power, for example. The microstructure power device of one embodiment is a microelectromechanical system (MEMS)-based device that operates to harvest energy from mechanical vibrations. Embodiments of the RFID tag powered by the microstructure power device can further provide energy storage capabilities in which the energy harvested from mechanical vibrations is stored and subsequently applied for use in reading, writing, and/or other operations.
According to one embodiment, the microstructure power device uses electrostatic energy harvesting techniques in which the capacitance of a capacitor is varied by mechanical vibrations. In another embodiment, the microstructure power device can use piezoelectric energy harvesting techniques in which mechanical energy from mechanical vibrations is used to strain a piezoelectric material. In yet another embodiment, the microstructure power device can use electromagnetic energy harvesting techniques in which a magnetic field converts mechanical energy from mechanical vibrations to electrical energy.
According to one embodiment, the RFID tag can be read (and/or written to) while the RFID tag is in motion, such as when a product onto which the RFID tag is affixed is placed on a conveyor belt, forklift, or other machinery. Such machinery produces mechanical vibrational energy that can be harvested by the microstructure power device and then used to power the RFID tag for reading/writing operations. The RFID tag can also be read (and/or written to) after motion from the machinery has ended if the RFID tag has been provided with an energy storage device that has stored the previously harvested energy from the mechanical vibrations. Alternatively or additionally, ambient mechanical vibrational energy from buildings or other environments may also be sufficient to provide power to the RFID tag for reading/writing operations, even if the RFID tag is not physically present on moving machinery (e.g., the product having the RFID tag affixed thereto may be sitting on a storage shelf). Thus, the RFID tag can be provided with capability to harvest energy (and thus be read or written to) during many different situations and environments when mechanical vibrational energy is present.
Referring first to
The RFID tag 102 typically acts as a transponder, transmitting responses (to an interrogation signal) that encode information or data stored in memories of the RFID tag 102. Some of the RFID tags 102 may also be written to, and may employ security measures and/or encryption techniques. The structure and method of operation of the RFID tag 102, as well as RFID interrogators and other RFID readers are well known in the art and need not be discussed in great detail hereinafter.
The RFID tag 102 includes or is otherwise coupled to an RF antenna 108. According to an embodiment, since the microstructure power device 104 has been provided for energy harvesting, the RFID tag 102 need not implement the complex antenna design of conventional passive RFID tags that need to perform the multiple tasks of signal reception/transmission plus acquisition of power from an RF field. Instead, the antenna 108 of one embodiment can be designed solely for transmission and reception of RF signals for data communication.
Such an embodiment of the antenna 108 can be simpler in design (such as a dipole antenna), thereby providing cost reduction benefits. Furthermore, an embodiment of the antenna 108 that is designed primarily for signal transmission/reception (and not further designed for RF power acquisition) would have increased range and performance, reduce the overall size of the RFID tag 102, and improve omnidirectional performance.
Moreover, RFID tags having conventional antennas that are designed for the multiple purposes of signal transmission/reception and RF power acquisition may be more sensitive to physical impacts on the RFID tag, such as impacts against the RFID tag during shipping and handling. Minor damage to such conventional antennas may reduce or completely remove the RF power acquisition capability of the RFID tag, thereby making the RFID tag useless, even if the damage itself does not significantly affect or otherwise damage the signal transmission/reception capability of the antenna. In contrast, the RFID tag 102 of one embodiment may continue to function adequately even if minor damage to the antenna 108 occurs, since the antenna 108 is not being relied upon to provide power to the RFID tag 102.
In another embodiment, the antenna 108 can be designed for signal transmission/reception plus power acquisition from an RF field. In such an embodiment, the power derived from the energy harvested by the microstructure power device 104 can be used to increase and/or enhance range and performance of the RFID tag 102.
The RFID tag 102, the microstructure power device 104, and the related structures shown in
In another embodiment, the RFID tag 102 and the microstructure power device 104 can comprise different or discrete ICs, chips, or other assemblies. In such an embodiment, the substrate 110 of
The system 100 includes an automatic data collection device 112 to read from or write to the RFID tag 102 using one or more wireless signals 114. The automatic data collection device 112 of one embodiment comprises a handheld device. The automatic data collection device 112 of another embodiment can comprise a stationary device, such as a fixed device that interrogates RFID tags 102 affixed to items moving on a conveyor belt.
However, with the embodiment of the system 200 in
The number N of microstructure power devices 204 in the embodiment of
The platform 304 can comprise a conveyor belt, forklift, inventory shelf, vehicle cargo hold, pallet board, shipping container, or other structure onto or into which items 302 are typically placed. In the case of a conveyor belt, forklift, vehicle cargo hold, or other types of platforms associated with machinery, such machinery produces mechanical vibrations (e.g., actively induced vibrations or pressure waves such as those commonly denoted as sound) that are transferred onto the platform 304, as symbolically shown at 306 in
The mechanical vibrations 306-310 of
With the environment 300 depicted in
The microstructure power device 102/202 comprises at least one base element 400 positioned in proximity to a cavity 402. The base element 400 has at least one movable element 404 mounted thereon that is adapted to move within the cavity 402 in response to mechanical vibrations. The base element 400, cavity 402, movable element 404, and other features of the microstructure power device 102/204 are shown in further detail in
For purposes of explanation, a plurality of six (6) movable elements 404 (and their associated base elements 400 and cavities 402) are shown in
With specific reference now to
It is appreciated that the movable elements 404 need not necessarily have synchronized and equal-magnitude movement. For instance, some movable elements 404 may have their right ends in the upward position, while other movable elements 404 have their right ends in the downward position, while still other movable elements 404 have positions in between these two extreme positions. As another example, some movable elements 404 may experience a greater magnitude and/or frequency of movement during a period of time in response to mechanical vibrations, as compared to other movable elements 404 in the same microstructure power device 102/204.
In an embodiment, the microstructure power device 102/204 includes an unpatterned silicon backside wafer 502 on which the base elements 400 are formed. In an embodiment, the base elements 400, the movable elements 404, and the torsional springs 500 are made from a silicon material present in a layer 504, such as a MEMS wafer.
A layer 506, such as patterned silicon topside wafer, is located above the layer 504. The layer 506 includes the cavities 402, which are defined by silicon structures 508. In an embodiment, the silicon structures 508 can be manufactured using deposition and/or etching techniques, and further, air or other suitable gas can be present in the cavities 402. Portions of the conductors 106 (such as conductive pads or traces) can also be present in the layer 506.
A patterned (or unpatterned) seal 510 overlies the layer 506. The seal 510 protects the underlying components from dust, corrosion, scratching, or other physical and/or environmental effects that can cause damage. An example material for the seal 510 is glass, and other types of material (such as plastic) can be used.
An embodiment of the microstructure power device 102/204 is based on electrostatic (capacitive) energy harvesting, which relies on the changing capacitance of vibration-dependent variable capacitors. As depicted in
The structures 602 interleave with the structures 600 such that variable capacitances 604 exist between opposing surfaces of the structures 600 and 602, which form capacitor plates. In operation, the structures 600 and 602 are initially charged, thereby initially charging the capacitor plates. Mechanical vibrations then cause the structures 602 to undergo motion (symbolically depicted by the arrows 606). As the structure 602 changes positions due to mechanical vibrations, the capacitor plates separate (thereby varying the capacitances 604) and mechanical energy is transformed into electrical energy.
In one embodiment, the structures 602 and 604 can be fabricated as MEMS variable capacitors through relatively mature silicon micro-machining techniques. This electrostatic (capacitive) energy harvesting technique described above produces higher and more practical output voltage levels than electromagnetic techniques for energy harvesting, and further provides moderate power density.
As shown in
In one embodiment, the energy harvested using the microstructure power device 104/204 of
In one embodiment, the harvested energy can also be used to enhance range and performance of the RFID tag 102/202. For instance, if the antenna 108/208 is a “hybrid” design that is capable of power acquisition from an RF field and signal transmission/reception, the harvested energy from the microstructure power device 104/204 can be used as auxiliary power to enhance the range of signal transmission/reception or for other purposes and operations that involve power consumption.
In another embodiment, such as shown in
In the embodiment of
The various embodiments described above implement electrostatic (capacitive) energy harvesting techniques for the microstructure power device 104/204. It is appreciated that other types of energy harvesting techniques may be used in other embodiments to obtain energy from mechanical vibrations.
In
In one embodiment, the piezoelectric material 802 comprises a cantilevered beam structure having at least one mass 808 at a distal end of the beam structure. A support structure 804 is provided at a proximate end of the beam structure. When mechanical vibration is present, the mass 808 and the piezoelectric material 802 move in a motion depicted by the arrow 806.
Example piezoelectric energy harvesting techniques and structures that can be implemented in various embodiments are disclosed in Tanielian (U.S. Pat. No. 6,771,007), Oliver (U.S. Pat. No. 6,407,484), Kimura (U.S. Pat. No. 5,801,475), and Tuttle (U.S. Pat. No. 5,300,875). These patents are incorporated herein by reference in their entireties.
In
A coil 906 is attached to the oscillating mass 904 and traverses through a magnetic field that is provided by a magnet 908. The coil 906 thus travels through a varying amount of magnetic flux, thereby inducing a voltage V according to Faraday's Law.
In some embodiments, certain operations of the method 1000 can be implemented in software or other machine-readable instruction stored on a machine-readable medium and executable by a processor. For example, application of the harvested energy for reading, writing, or other operations of the RFID tag 102/202 or the automatic data collection device 112/212 can be performed using software.
At a block 1002, the microstructure power device 104/204 is coupled to the RFID tag 102/202. In one embodiment, the operations at the block 1002 are performed during the manufacturing stage by: manufacturing the embodiments of the microstructure power device 104/204 and components thereof shown in
At a block 1006, the RFID tag 102/202 having the microstructure power device(s) 104/204 coupled thereto is affixed to the item 302 of
In a block 1010, the microstructure power device 104/204 harvests energy from mechanical vibrations. Accordingly, the RFID tag 102/202 inherently becomes “activated”, substantially without requiring a discrete power source (such as a battery) as a source for power different from the power derived from mechanical vibrations and/or without obtaining energy from an RF field. The RFID tag 102/202 is thus autonomous and capable of indefinite “active” operation independently of a discrete power source (and therefore not requiring battery maintenance).
In some embodiments, energy storage capabilities and operations may be provided at a block 1012. For example and with reference to
In other embodiments, reading from and/or writing to the RFID tag 102/202 using the harvested energy at a block 1014 can be performed substantially contemporaneously with the energy harvesting. Thus, as the energy is harvested, such harvested energy is immediately put to use to provide power for reading/writing and related operations.
At a block 1016, the harvested energy may be applied for other purpose, alternatively or additionally to the reading and writing operations at the block 1014. For example, in embodiments where the RFID tag 102/202 is a passive RFID tag that obtains power from an RF field, the harvested energy can be used to enhance the range and/or other capabilities of such an RFID tag by providing a power boost or other auxiliary power to supplement the power obtained through the RF field. In some embodiments, the energy harvested from mechanical vibrations can be used for other purposes, such as encryption, updating stored data, and so forth.
From the above description of embodiments, the MEMS-based or other type of microstructure power device 104/204 is capable of providing power to the RFID tag 102/202, thereby providing an alternative to passive RFID tags that rely on power obtained from an RF field. Relatively low cost, higher performance, and smaller-sized RFID tags 102/202 are thus possible, since the requirements for providing, maintaining, and replacing a discrete battery (of an active RFID tag) and the requirements for the complex multiple purpose antenna design (of a passive RFID tag) are eliminated.
The smaller size of the RFID tag 102/202 can further allow individual products (such as consumer products) to be tagged, rather being constrained to being applied to case-level or container level tagging. As a result, more detailed tracking and identification of individual products are possible.
All of the above U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, are incorporated herein by reference, in their entirety.
The above description of illustrated embodiments, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed. While specific embodiments and examples are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the invention and can be made without deviating from the spirit and scope of the invention.
These and other modifications can be made to the embodiments in light of the above detailed description. The terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification and the claims. Rather, the scope of the invention is to be determined entirely by the following claims, which are to be construed in accordance with established doctrines of claim interpretation.