Monday, August 10, 2009

The Simple RFID Explained

What is RFID?

Radio frequency identification, or RFID, is a generic term for technologies that use radio waves to automatically identify people or objects. There are several methods of identification, but the most common is to store a serial number that identifies a person or object, and perhaps other information, on a microchip that is attached to an antenna (the chip and the antenna together are called an RFID transponder or an RFID tag). The antenna enables the chip to transmit the identification information to a reader. The reader converts the radio waves reflected back from the RFID tag into digital information that can then be passed on to computers that can make use of it.
Is RFID better than using bar codes?

RFID is not necessarily "better" than bar codes. The two are different technologies and have different applications, which sometimes overlap. The big difference between the two is bar codes are line-of-sight technology. That is, a scanner has to "see" the bar code to read it, which means people usually have to orient the bar code toward a scanner for it to be read. Radio frequency identification, by contrast, doesn't require line of sight. RFID tags can be read as long as they are within range of a reader. Bar codes have other shortcomings as well. If a label is ripped or soiled or has fallen off, there is no way to scan the item, and standard bar codes identify only the manufacturer and product, not the unique item. The bar code on one milk carton is the same as every other, making it impossible to identify which one might pass its expiration date first.

Will RFID replace bar codes?
It's very unlikely. Bar codes are inexpensive and effective for certain tasks, but RFID and bar codes will coexist for many years.

Is RFID new?
RFID is a proven technology that's been around since at least the 1970s. Up to now, it's been too expensive and too limited to be practical for many commercial applications. But if tags can be made cheaply enough, they can solve many of the problems associated with bar codes. Radio waves travel through most non-metallic materials, so they can be embedded in packaging or encased in protective plastic for weatherproofing and greater durability. And tags have microchips that can store a unique serial number for every product manufactured around the world.

What is the purpose of RFID?
RFID allows data to be transmitted by a product containing an RFID tag microchip, which is read by an RFID reader. The data transmitted can provide identification or location information about the product, or specify information such as date of purchase or price.

What is the advantage of using RFID technology?
No contact or even line-of-sight is needed to read data from a product that contains an RFID tag. This means no more checkout scanners at grocery stores, no more unpacking shipping boxes, and no more getting keys out of your pocket to start your car. RFID technology can also work in rain, snow and other environments where bar code or optical scan technology would be useless.

Are there any standards for RFID?
Yes. International standards have been adopted for some very specific applications, such as for tracking animals and for smart cards, which require encryption to keep data secure. Many other standards initiatives are under way. The International Organization for Standardization (ISO) is working on standards for tracking goods in the supply chain using high-frequency tags (ISO 18000-3) and ultra-high frequency tags (ISO 18000-6). EPC global, a joint venture set up to commercialize Electronic Product Code technologies, has its own standards process, which was used to create bar code standards. EPC global has submitted the second-generation UHF EPC protocols to ISO, and it has been approved as ISO 18000-6C, an international standards.

What are the types of RFID Standards?
ISO 15693-Smart Labels
ISO 14443-Contactless payments
ISO 11784-Livestock
ISO 18000-Various frequencies, various applications

What are the types of RFID applications?
- Livestock tracking
- Automotive immobilizer
- Contactless payments
- Anti-theft
- Library application
- Speed Pass
- Control Access
- Production/Inventory tracking
- Retail
- Asset Management

What is the difference between low (LF), high (HF), and ultra-high frequencies (UHF)?
Just as your radio tunes in to different frequencies to hear different channels, RFID tags and readers have to be tuned to the same frequency to communicate. RFID systems use many different frequencies, but generally the most common are low-frequency (around 125 KHz), high-frequency (13.56 MHz) and ultra-high-frequency or UHF (860-960 MHz). Microwave (2.45 GHz) is also used in some applications. Radio waves behave differently at different frequencies, so you have to choose the right frequency for the right application

Application for different frequencies:
LF Applications (125KHZ): Access control, livestock, race timing, pallet tracking, automotive immobilizers, pet identification

HF Applications (13.56MHZ): Supply chain, wireless commerce, ticketing, product authentication, clothing identification, library book identification, smart cards

UHF Applications (860-960MHZ): Supply chain, Tool Tags, RTLS, EPC Case and Pallet
What are the transponder characteristics?
RFID tags are tiny microchips with memory and an antenna coil, thinner than paper and some only 0.3 mm across. RFID tags listen for a radio signal sent by a RFID reader. When a RFID tag receives a query, it responds by transmitting its unique ID code and other data back to the reader. Basically there are 3 kinds of tags- Active, Passive and Semi Passive.

What is the difference between a passive, semi-passive and active RFID?
Active RFID uses an internal power source, such as a battery, within the tag to continuously power the tag and its RF communication circuitry. Active RFID allows extremely low-level RF signals to be received by the tag (since the reader/interrogator does not power the tag), and the tag can generate high-level signals back to the reader/interrogator. Active RFID tags are continuously powered, whether in the reader/interrogator field or not, and are normally used when a longer tag read distance is desired.

Passive RFID relies on RF energy transferred from the reader/interrogator to the tag to power the tag. Passive RFID tags reflect energy from the reader/interrogator or receive and temporarily store a small amount of energy from the reader/interrogator signal in order to generate the tag response. Passive RFID requires strong RF signals from the reader/interrogator, and the RF signal strength returned from the tag is constrained to very low levels by the limited energy. Passive RFID tags are best used when the tag and interrogator will be close to one another.

Semi-passive RFID uses an internal power source to monitor environmental conditions, but requires RF energy transferred from the reader/interrogator similar to passive tags to power a tag response. Semi-passive RFID tags use a process to generate a tag response similar to that of passive tags. Semi-passive tags differ from passive in that semi passive tags possess an internal power source (battery) for the tag's circuitry which allows the tag to complete other functions such as monitoring of environmental conditions (temperature, shock) and which may extend the tag signal range.

What’s the difference between read-only and read/write tags?
Chips in RF tags can be read-write or read-only. With read-write chips, you can add information to the tag or write over existing information when the tag is within range of a reader, or interrogator. Read-write tags are useful in some specialized applications, but since they are more expensive than read-only chips, they are impractical for tracking inexpensive items. Some read-only microchips have information stored on them during the manufacturing process. The information on such chips can never been changed. A more flexible option is to use something called electrically erasable programmable read-only memory, or EEPROM. With EEPROM, the data can be overwritten using a special electronic process.
How much information can an RFID tag store?
Tags are available with storage capabilities from 512 bytes to 4MB. It largely depends on vendor and whether the tag is passive or active. Data stored in a tag will be determined by the application of the system and appropriate standards. For example, a tag could provide identification for an item being manufactured, goods in transit, or even the short-range location and identity of a vehicle, animal, or individual. This fundamental data often is referred to as a "license plate code," similar to the information that is stored on a bar code label. When linked to a database, additional information may be accessed through the reader such as item stock number, current location, status, selling price, and batch code. Alternatively, an RFID tag may carry specific information or instructions immediately available upon reading, without the need to reference a database to determine the meaning of a code. For example, the desired color of paint on a car that is entering the paint assembly area on the production line, or a manifest to accompany a shipment of goods.

Transponder, smart label, Tag. What's the difference?
Initially, in the technical field, transponder was the term used to designate an electronic module which is able to Transmit information and respond with information. Recently, different fields in which Radio Frequency Identification is prevalent have developed a new jargon to designate the same thing, such as Smart Label or Tag. "Smart labels" are a particularly innovative form of RFID tag and operate in much the same way. However, a smart label consists of an adhesive label that is embedded with an ultra-thin RFID tag "inlay" (the tag IC plus printed antenna). Smart labels combine the read range and unattended processing capability of RFID with the convenience and flexibility of on-demand label printing. Smart labels also can be pre-printed and pre-coded for use. In on-demand applications, the tag inlay can be encoded with fixed or variable data and tested before the label is printed, while the label can contain all the bar codes, text, and graphics used in established applications. Smart labels are called "smart" because of the flexible capabilities provided by the silicon chip embedded in the tag inlay. A read/write smart label also can be programmed and reprogrammed in use, following initial coding during the label production process.

Can I tag metal objects? Can I tag items that have high-water content?
Yes. Radio waves bounce off metal and are absorbed by water at higher frequencies. While that can make tracking metal objects or those with high water content problematic, well-planned system design and engineering can solve these issues.

What is an RFID reader?
A reader is basically a radio frequency transmitter and receiver, controlled by a microprocessor or digital signal processor. The reader, using an attached antenna, captures data from tags then passes the data to a computer for processing. As with tags, readers come in a wide range of sizes and offer different features. Readers can be affixed in a stationary position (for example, beside a conveyor belt in a factory or dock doors in a warehouse), portable (integrated into a mobile computer that also might be used for scanning bar codes), or even embedded in electronic equipment such as print-on-demand label printers

What are the reader characteristics?
• Stationary or handheld (different RFID Reader Modules)
• Weather-proof or industrialized
• Typical read ranges vary from a few centimeters to a few meters
• Read range is dependent upon:
o Broadcast signal strength
o Size of broadcast antenna
o Size of transponder antenna
o The environment factor: Metallic, Liquid
• Multi-frequency readers

RFID read-only readers These devices can only query or read information from a nearby RFID tag. These readers are found in fixed, stationary applications as well as portable and handheld varieties.

RFID read-write readers Also known as encoders, these devices read and also write (change) information in an RFID tag. Such RFID encoders can be used to program information into a blank RFID tag. A common application is to combine such a RFID reader with a barcode printer to print smart labels. Smart labels contain a UPC bar code on the front with an RFID tag embedded on the back.

What are the types of antenna characteristics?
- Transmits and receives RF signals
- Typically made of copper or aluminum, new technologies for printed antennas
- Stationary or handheld
- Weather-proof/industrialized
- Fixed or tunable

What are the RFID system considerations?
Read distance requirements
- Long read range
- Short read range

- All frequencies have their pros and cons

ISO standards
- Proprietary or standards-based

Government regulations
- Varies from country to country

Multiple Tag Reading in Same Field
- Anti-collision

Sensitivity to Orientation
- A single orientation or Omni-directional

Hardware Set-up
- Environment can affect performance


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