Patent Application
20070024447
The present application claims the foreign priority of Taiwan Application Serial Number, 94125975 which was filed on Jul. 29, 2005.
The present invention relates generally to radio energy transmission, and more specifically related to transporting radio energy through a set of containers for radio frequency identification systems.
A radio frequency identification (RFID) system uses RF transmission to identify, categorize, locate and track elements. It is made up of two primary components: a transponder or the RFID tag and a reader. The tag is a device that generates electrical signals or pulses interpreted by the reader. The reader is a transmitter/receiver combination (transceiver) that activates and reads the identification signals from the transponder.
RFID tags are considered to be intelligent bar codes that can communicate with a networked system to track every element associated with a designated tag. RFID tags will communicate with an electronic reader that will detect the “tagged” element and further connects to a large network that will send information on the elements to interested parties such as retailer and product manufacturers. For example, the tag can be programmed to broadcast a specific stream of data denoting identity such as serial and model numbers, price, inventory code and date. Therefore, the RFID tags are expected to be widely used in the wholesale, distribution and retail businesses.
The RFID tag is an integrated circuit that is coupled with an antenna to receive incoming RFID radiated power and to transmit data. The circuit contains memory that stores the identification code and other pertinent data to be transmitted when the microprocessor is activated or interrogated using radio energy from the reader. RFID systems can be further categorized by their tag characteristics being active or passive. Active tags include a power source such as a battery. The battery may be built-in or connected to the tag. Advantages of an active tag are a longer read range and a reduced reader power requirement. Passive tags have no on-board power source, but do have a chip and an antenna. Thus, they are powered electromagnetically by the reader radiated signal. The advantages of passive tags are that they cost less, are considerably smaller and lighter than the active tag, and their lifetime is virtually unlimited. However, they have a short read range, and a higher powered reader is required to interrogate or activate them.
Compared to passive bar code based labels, the RFID tags are much more “active”. There are traditionally two types of RFID tags, the inductively-coupled RFID tags and the electromagnetic-coupled RFID tags. Inductive RFID tags are powered by the magnetic field generated by the reader. After the tag picks up the magnetic energy, the tag communicates with the reader. The tag then modulates the magnetic field in order to retrieve and transmit data back to the reader. Data is transmitted back to the reader, which further connects to a computer network for processing the data received.
Electromagnetic-coupled RFID tags do away with the metal coil in that they use the incoming RF signal to charge a capacitor. An electromagnetic-coupled tag has a microprocessor, which can also store certain bits of information, which would allow for trillions of unique numbers that can be assigned to products or elements associated with such tags. There is an antenna component that is built into the tag using, for example, a conductive carbon ink printing process. The conductive carbon ink may be printed to a paper substrate or thin film through conventional printing means. The microprocessor is attached to the printed electrodes on the back of the label, creating a disposable tag that can be integrated on conventional product labels.
The disadvantage to the inductively-coupled tag is that it has a very limited range. The electromagnetic-coupled tag can function at a much longer distance. However, in order for a system of multiple communicating tags in complicated environments to work, the range still needs to be boosted. Companies have developed RFID tags that tend to meet these needs, but they are more expensive than what is ultimately needed in the marketplace.
A reader also contains an RF antenna, transceiver and a micro-processor. The transceiver sends activation signals to and receives identification data from the tag. The antenna may be enclosed with the reader or located outside the reader as a separate piece. The reader may be either a hand-held or a stationary component that checks and decodes the data it receives.
In order for an RFID system to work, each product or element associated with a tag may have to be given a unique product number. MIT's Auto-ID Center is working on an Electronic Product Code (EPC) identifier that could replace the UPC. Every tag could have such an identifier containing 96 bits of information, including the product manufacturer, product name and a 40-bit serial number. Using this system, an RFID tag would communicate with a network, called the Object Naming Service, which would retrieve information about a product and then direct information to the manufacturer's computers.
One of the biggest problems facing RFID applications is multiple item scanning. When several tags are read at the same time and these tagged items are close together, one tag's transmission interferes with that of another. In such an autonomous wireless environment with multiple items that are being interrogated and responding at the same time, the resulting signal interference can cause fading problems. For example, when pluralities of containers are provided in a pile for scanning, some of these containers may be containing metal structures that will tend to block an incoming RF signal. Or, the containers may hold materials that cause multi-path of signals or even contain material that acts as electromagnetic absorber.
In most wireless systems with presented interferences, the quality of a desired signal is improved by increasing its signal-to-noise ratio so that the specific signal can be properly decoded. In the multiple articles environment, due to the rich interference, an increased reader signal level will tend to only make the problem worse by exciting more tags and enhancing the multi-path situation.
Therefore, desirable in the art of RFID world is an improved system for identifiably reading or detecting items tagged by RFID tags in a multiple article environment.
This invention provides a radio frequency identification (RFID) system comprising at least one reader module for radiating RF energy, a plurality of predetermined containers tagged by a plurality of RFID tags for receiving the radiated RF energy, wherein one or more containers are equipped with at least one conducting surface associated with at least one container side piece thereof so that when the plurality of the predetermined containers form a pile, an RF energy propagation channel network is formed comprising one or more propagation channels constructed by at least two conducting surfaces between two containers for confining and propagating the RF energy there between.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
The present invention provides a radio energy propagation channel network to define predetermined propagation channels that allow sufficient energy to be received by the RFID tag antenna.
An RFID system is basically a wireless system that is used to identify RFID-tagged items based on the specific tag information recorded on the RFID tags. Each tag is activated by an interrogating signal transmitted wirelessly through an RF frequency band that charges up an internal capacitor within the RFID tag. As this capacitor is charged by the incoming RF signal, the tag's IC input impedance is modulated with the recorded information. This modulates the backscatter return from the tag antenna so that an interrogating source such as a reader module can determine the needed response. This information is then used by the reader to define the disposition of the tagged items.
As well-known in the industry, one major problem that still remains in RFID applications is the very complex propagation path in that the reader desires to communicate with tagged items such as containers that are surrounded not by free space, but by other items or containers. If the surrounding containers hold metal structures, they will tend to block the incoming RF signal from reaching certain containers that are surrounded by them. In other cases, the surrounding containers may hold materials that cause tremendous multi-path effects of a very complex nature or even contain materials that act as electromagnetic absorber that greatly attenuates the incoming RFID signal. Therefore, the wireless link between the reader and the desired tagged items is broken or nearly-broken if an improved RF signal propagation path is not better-defined that will allow sufficient energy to be received by the RFID tagged items, or more specifically, by the tag antenna.
For illustration purposes, the present invention is illustrated in the context of providing the RF signal propagation paths in a multi-container environment in which a plurality of containers are placed together in a pile together. Since the containers are made of low-loss dielectric material such as cardboard, the paper-based cardboard acts very much like free space in that it causes very little attenuation of the RF signal at the RFID frequencies. Since the containers are “piled” up together, the predetermined thicknesses of the surfaces of the containers naturally create space between these containers.
Referring to an area confined in the rectangular box 112, this is where two containers border on each other. It is assumed that the interior paper-based surfaces of every container have additional conducting surface placed or coated thereon. The RF energy propagation channel is formed by having the conducting surface 104A from the container on the top and the conducting surface 104B from the bottom container with line 114 showing the seam between the two containers. This channel will direct the energy to flow along the cardboard as indicated by the arrows. A plurality of this kind of channel forms an energy propagation channel network. As such, the desired RF energy flows through the propagation channel network taking a path that is independent of the contents of the containers. It is understood that the conducting surface can be placed on or otherwise associated with the interior or exterior surface of the container. In fact, the conducting surface can be associated with the container side piece by being embedded between the interior and exterior surfaces of the container. Further, this can be a broadband solution because the propagation path follows a guided structure that does not have a lower frequency cutoff provided that the incident signal is polarized normal to the boundaries of the channel. The RFID tag; antenna 108, if properly designed, will receive sufficient signal-to-noise performance to allow it to function properly even in very complex pile configurations.
The RF energy propagation channels formed between the containers can be of various configurations. For example, even if the containers are of different sizes, or the containers are arbitrarily located or positioned, or even filled with any possible contents, the energy propagation channel network can still be formed automatically through the “piling” of the containers, and the parallel or substantially parallel surfaces of each segment of the energy propagation channels causes the energy to flow in the propagation paths that are isolated from the contents.
The two conducting surfaces forming the energy propagation channel can be associated with one side piece of a container. As opposed to the example illustrated in
This pile of containers illustrates that although the energy propagation channel network can be formed by containers having all side pieces covered by conducting materials, it can still work with containers of other configurations. Packaging companies can decide what type of containers should be used based on the determination of the content carried by the containers. This also illustrates that the energy propagation channel network should be loosely defined and does not require the RF energy to travel between two closely placed conducting surfaces. For instance, in a pile of containers, there can be only one container that has all its side pieces associated with conducting surfaces, and it should be recognized that an RF energy propagation channel network exists as the RF energy gets “reflected” from the surfaces and penetrates other containers in the pile.
As illustrated above, the surfaces are fixed at a relatively-small distance apart, even though a low-loss spacer may be used to allow more RFID radiated energy to be received by the tag antenna. In order to provide sufficient energy through this small spacing, the RF signals propagating therein will be polarized normal to the surfaces in order to satisfy the fundamental boundary conditions. Thus, this normal polarized signal will provide the best result.
The above illustration provides many different embodiments or embodiments for implementing different features of this invention. Specific embodiments of components and processes are described to help clarify the invention. These are, of course, merely embodiments and are not intended to limit the invention from that described in the claims.
Although the invention is illustrated and described herein as embodied in one or more specific examples, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention, as set forth in the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 94125975 | Jul 2005 | TW | national |
