RFID Tag Categories | RFID Construction | Applications | Privacy Issues | Chipless RFID Technology
RFID, which is an acronym for Radio Frequency Identification, is not a new technology. It was first used in the late 1960's, but it has only become more widespread with advances in technology.
RFID Systems consist of a transponder, also known as a tag, which is basically a microchip connected to an antenna. The tag is mounted to an item, such as a pallet of goods in a warehouse, and a device called a reader communicates with the tag via radio waves. Depending on the type of tag that is used, the reader can receive detailed information or it can receive data as simple as an identification number.
RFID is similar to barcode systems in which data, such as a price, is accessed when the barcode is read. The main difference is that the barcode must come in direct contact to an optical scanner/reader and the RFID tag can transmit to the reader via radio waves and does not have to be in direct contact. An RFID reader can receive data from as many as 1,000 tags per second.
The radio signals can go through many non-metallic substances such as rain, fog, snows, dirt and grime, painted surfaces, etc. This gives RFID tags a distinct advantage over optically read items, such as barcodes, which would be useless under similar conditions.
The many uses for RFID technology include:
- Smart labels and security labels
- Product and inventory management
- RFID chips in car keys for security
- Theft control
- Placement on pharmaceuticals to prevent counterfeited drugs from entering the legal supply chain
- Increased efficiency in admissions into entertainment or sporting events
- Increased efficiency in toll road payments
- Monitoring the whereabouts of luggage, library books, livestock, etc.
It is predicted that RFID use will continue to increase. It is unlikely to ever be as cost-effective as barcoding, but it will become dominant in areas where barcoding and other optically read technologies are not effective.
RFID Tag Categories
The basic types of RFID tags can be classified as read/write and read only. The data stored on read/write tags can be edited, added to, or completely rewritten, but only if the tag is within the range of the reader. The data stored on a read only tag can be read, but cannot be edited in any way. Read/write tags are much more expensive than read only tags, so they are not used for tracking most commodity items.
RFID tags are further categorized as:
- Active tags, which contain a battery that powers the microchip and allows it to transmit a signal to the reader.
- Semi-active (or semi-passive) tags, which contain a battery to run the circuitry of the chip, but must draw power from the magnetic field created by the reader in order to communicate with the reader.
- Passive tags, which rely solely on the magnetic field created by the radio waves sent out by the reader to create a current that can be received by the antenna within the passive tag.
RFID Tag Components
RFID tags consist of a microchip connected to an antenna, which is constructed of a small coil of wires. The assembly is usually covered with a protective layer (such as a laminated card), which is determined by the type of application. The RFID tag can be a passive tag or an active tag. The RFID tag is also known as an inlay.
Components of passive RFID system:
- An antenna is attached to a microchip.
- The antenna allows the chip to transmit information to a reader, which also has an antenna.
- The reader is the device that actually sends out the radio waves to create a magnetic field. A passive RFID tag draws its power from this magnetic field, which powers the circuits in the microchip allowing it to transmit data back to the reader.
- Reader transmits to a computer system.
- The computer passes data onto a network.
- Software determines how the data received should be used.
The most expensive read/write, active RFID transponders may have microchips with a memory capacity of up to one megabyte (1,000,000 characters). Most tags are inexpensive, passive transponders that can store only 32 to 128 bits (characters) of information or less, so an identification number is basically the only data that the read-only tag will contain. When the number is read, detailed information stored in a database in a computer can be accessed. This is similar to a barcode system in which data, such as a price, is accessed when the barcode is read. The main difference is that the barcode must come in direct contact to an optical scanner/reader and the RFID tag can transmit to the reader via radio waves and does not have to be in direct contact.
The antenna allows the chip to receive and relay information, such as an ID number of an individual product. Some antennas are constructed of metal and are etched or stamped from metal, such as copper. Other types of antennas are printed. Advances in technology are allowing printed antennas to achieve the functionality of traditional materials and printed antennas are less expensive. One of the most popular methods of printing antennae is with the use of silver conductive inks printed on plastics substrates or paper. Testing of RFID antennae is usually performed with ohmmeters, milliohm meters, RF network analyzers, impedance-measuring equipment, and others.
RFID Tag Shapes and Sizes
RFID tags can be manufactured in several different shapes and sizes depending on the type of application in which they will be used.
- Some are the size of a pencil lead or are less than a half-inch in length and can be inserted under the skin of animals and livestock.
- Screw-shaped tags are used to identify specific trees.
- Rectangular RFID tags found in some products are used as an anti-theft device.
- Large, heavy duty tags that are several inches in length, width, and depth are used to track large containers or large vehicles such as trucks or rail cars.
RFID tags operate under different radio frequencies, depending on the application. The FCC of the US government determines the limits on power output of RFID systems as well as the different radio frequencies that can be used. Low, high, and ultra-high (UHF) frequencies are used with RFID transponders.
- Low and high frequency tags are less expensive than UHF and are best used for merchandise tracking, animal and livestock identification, and security access.
- Tags with UHF frequencies use more power than low and high frequency tags, but they have a greater range and the data transfer rate is faster. They are best suited for applications in which the tag and the reader have a more direct path with one another. Rail car tracking and automated toll booths are some of the uses.
The communication range between the RFID tag and the reader depends on the frequency, the antenna size of the tag, the antenna size of the reader, and the output power.
- Low and high frequency devices have communication ranges of a few inches to several feet, depending on the application.
- Ultra-high (UHF) may have ranges of 25 feet or more.
The radio signals can go through many substances such as rain, fog, snows, dirt and grime, painted surfaces, etc. This gives RFID tags a distinct advantage over optically read items, such as barcodes, which would be useless under similar conditions. An RFID reader can receive data from as many as 1,000 tags per second.
Quality control is a necessity because groups of manufactured inlays may have experienced some damage before they reach the printer or converter. The chips in the inlays can also be damaged during the printing or converting process, which renders the RFID tag useless. Special substrates can be used to limit the damage to the chips. Quality control after printing or converting is also important to ensure that none of the chips were damaged and will all be functional.
When RFID antennae are manufactured, they are usually tested with ohmmeters, milliohm meters, RF network analyzers, and impedance-measuring equipment. It is also important to remember that RFIDs are electronic devices and therefore should not be exposed to or stored near areas containing large amounts of electromagnetic or static energy.
The three most common uses for RFID tags are:
- Tracking items in production lines
- Tracking items in supply chains
- Enhancing security measures
In other industrial uses, tags attached to items for tracking during assembly or manufacture must be able to withstand heat, cold, etching processes, cleaning and degreasing procedures, moisture, dirt, and many other types of conditions and environments that would not be suitable for optically or magnetically read devices.
With most types of printed applications, such as labels, the user is unaware of the existence of the chip and antenna because of the different methods of concealing them on the document. Some printers (such as label printers) purchase inlays (containing the RFID) that are already manufactured and then incorporate them into their printed products.
Label printing is one of the fastest growing segments of the printing industry using RFID technology. Smart labels and electronic surveillance labels are being used for applications in which simple, optically read barcoding may not be suitable.
Smart labels contain RFID transponders to automatically capture data. The standard construction of a smart label consists of a pressure sensitive facestock, an inlay, which contains the radio frequency identification transponder, and a liner. The inlay is laminated between the facestock and the liner. The transponder contains an antenna and microchip.
The data from the smart label is accessed when the transponder passes by the reader. Radio wave lengths are picked up from the antenna and the data on the microchip is transferred to the reader and then passed on to a computer or printer. As the product moves from one stage to the next, its movements can be monitored and data can be updated when necessary. The smart label can identify, track in real-time, and authenticate a product.
Smart labels are used on all types of applications including supply chain management, production control, work-in-process, baggage identification and tracking, express delivery services, reusable container tracking, and security systems.
Equipment is available that is able to encode a separate RFID inlay and then bond it to the substrate after the label has been printed. A variety of label substrates can be used. This process eliminates the need for inserting transponders into blank label stock before the label stock is printed. Since the printing process can damage stock containing transponders, the process eliminates this problem by allowing the printing to happen first. The system creates a printing system that is on-demand. There is no need for special papers because the equipment can print on almost any label stock.
Other equipment is able to encode data on very thin UHF RFID transponders that are inserted into smart labels. The equipment immediately verifies the proper encoding. The equipment can then print text, graphics, or barcodes on the smart label to complete the application. The smart labels can be used for a number of warehousing, inventory, and supply chain tracking applications.
There are also compact desktop printers specifically design for RFID printing. The printers can read, write, and print labels that have an embedded RFID transponder.
The industry acceptance of smart labels has been slow. The RFID technology can improve performance and efficiency but is expensive to startup. As more companies commit to the use of this new technology it will become more widely accepted and many will benefit from its capabilities.
Electronic Article Surveillance (EAS) Labels
EAS labels are used as anti-theft devices. The label is used with EAS monitoring equipment to detect if an item is being removed without authorization. The EAS systems are used in retail stores, data centers, and libraries. When applied to products, the EAS label is capable of activating an alarm as it passes through an electronic surveillance detector, such as those found in retail store exits. When the product is purchased, the label is made inactive by the use of a deactivation device at the checkout station. Once the label is deactivated it is referred to as a "dead label". Labels that have not been deactivated are referred to as "live labels".
RFID is only one of the technologies used for EAS labels. Other common types are AM (Acousto Magnetic) and EM (Electro Magnetic). Each of the EAS systems has its own unique detection equipment that must be used to allow the system to work properly.
Because of the anti-theft protection they provide, the EAS labels and EAS systems allow more freedom for retail stores to display items that would usually be locked in display cases. This allows the consumer to examine the product more closely before purchasing.
Comparisons with Barcoding
RFID and barcode technology are similar in concept, but the two technologies have different methods for reading data. RFID reads data via radio waves and does not need a direct line of sight between the reader and the tag. Barcodes are read optically and do require a direct line of sight between the reader and the barcode.
Advantages of RFID systems over barcodes:
- It is not necessary to have a line of sight between the RFID tag and the reader as there is with a barcode and scanner.
- Information can be rewritten to the tag without having to see the tag. This is true even if the tag is mixed into other items that have been tagged.
- Nearly 100% of RFID tags are readable, unlike items that contain a printed barcode, which can become damaged with improper handling.
- The potential problems associated with substandard print quality of barcodes, which in turn leads to scanning and reading problems, are eliminated.
Other points to consider:
- Barcodes are universally accepted because they are very inexpensive and there are established standards for their use. RFID technology is more expensive and has fewer universal standards in the way they are used.
- Even if RFID technology becomes as widespread as barcoding, it will not totally replace the universally accepted barcode technology.
Other Print/Security Applications
Besides the various types of RFID labels that are being printed for product tracking and security, plastic cards and badges embedded with RFID transponders are being produced. Data from identification cards embedded with RFID tags can be read as people pass through a doorway. RFID tags embedded in security badges offer an alternative method for controlling access to sensitive information or limiting access to specific areas.
When used with product and inventory control, a computer keeps track of the data received from the transponders/tags through the reader and can trigger reorders based on the adjusted inventory levels. Antennas can be built into warehouse doorframes in order to receive data as merchandise, cartons, and pallets of goods containing an RFID tag pass, through the doorway.
RFID costs may not become low enough for the tags to be used on all types of products and services. It may not be cost effective to include the tags with every item if the items are inexpensive commodity items, but the tags can be very useful to track full pallets of commodities for inventory control.
RFID tags can be used for a number of applications in the transportation industry for monitoring and tracking of vehicles and products.
RFID systems can be configured for rail car identification:
- The tags are installed underneath the rail cars.
- The antennae are mounted between or near the tracks.
- The readers are usually located in a building no more than 100 feet away.
Commercial trucking facilities also use RFID systems to monitor truck movements in and out of a main terminal.
RFID systems are very useful in the automobile manufacturing industry in tracking individual vehicles through the assembly process. RFID systems are also being installed in toll booths to monitor the traffic.
Most airports track passenger baggage with barcoded labels or tags, but they are often damaged do to rough handling of the baggage. Barcoded tags that have been damaged because of rough baggage handling, may account for 10% of the total volume. All of these bags must be accounted for manually, which can be a time consuming process. RFID systems can help to eliminate the problems that occur with unreadable barcodes.
When used for tracking bags at an airport, RFID tags contain a unique number assigned to the bag. Anyone with access to a reader could see the number, but any personal information could not be viewed because it is stored in a database and is not stored on the tag.
Many people mistakenly believe that RFID is similar to GPS (Global Positioning System) and can be used for detailed tracking, but RFID has a range of only a few feet so this isn't possible. Another misconception that people have is that the movement of products with RFID tags can be tracked even after the product is purchased. Most active RFID tags have a read range of about 25 feet, which means the RFID is basically useless outside of the retail store or business.
Security measures and safeguards used to protect consumer privacy when using RFID systems:
- The risk of spying or intercepting data that is transmitted via radio waves is reduced with the use of data encryption and over the air protocols.
- The protocols require both the reader and the eavesdropper to be within range of the tag.
- The reader changes radio frequencies rapidly and at random, so it is difficult for a potential eavesdropper to follow the reader.
- Although it is possible for tags to be counterfeited, it is not very practical because of built-in safeguards, such as the ability of the RFID readers to verify authenticity of the tags.
Chipless RFID Technology
Systems are now available that provide RFID technology for printed documents without the need for a microchip. Some of the systems involve the use of aluminum fibers, which are embedded into paper or packaging materials. The fibers reflect a signal, which are interpreted as data in a computer.
Another chipless system involves the use of materials made up of very small chemical particles that possess varying degrees of magnetism. The chemical particles become active when exposed to the electromagnetic waves from a reader. Each of the chemicals emits a unique signal that is received by the reader, which interprets the signal as a binary number. The system uses as many as 70 different chemicals, so there are 70 different signals. Each chemical has a specific position in the 70-digit number, which means that a unique binary number can be assigned to a document based on the mixture of chemicals that are used.
The small particles can be embedded in paper or they can be printed onto paper or almost any type of substrate. Printed barcodes can be created, which can be scanned from up to 10 feet away without the need for the barcode to be in line of sight of the reader. With slight modifications, this technology can be used with existing barcode systems, which helps to hold down the cost. Major upgrades of equipment are not necessary. The only areas where the system does not work very well are in areas containing large quantities of water or metal objects. Water absorbs RF signals and large quantities of metal reflect the signals.
Other security measures that can be used in conjunction with the system are:
- Photocopiers can be fitted with readers to prevent unauthorized copying.
- Some applications could require that a document be photocopied onto the same type of paper.
- Any institution wishing to protect documents could install readers at all exit points in the building, which would detect if any unauthorized persons were trying to leave the building with an original or copied document.
- The system can also be used for counterfeit prevention and for tracking manufactured products.
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