Radio Frequency ID (RFID) is one of the industry’s hottest technologies. There are large amounts of information published on the subject, stemming largely from the recent announcements of interest from major companies like Wal-Mart, the Department of Defense, International Paper, and Proctor and Gamble.
Radio Frequency Identification (RFID) technology can track and record the location, time of entry and exit from a designated area of persons and objects. RFID relies on radio frequency or “waves” between a card or tag and a reader in order to make identification and to carry out the tracking function. When the RFID card or tag enters, remains in, or leaves the magnetic field produced by the reader, the data store in the integrated chip of the card or tag is read and recorded by the reader. As RFID is a “contact-less” technology, it requires neither contact with a reader (as does magnetic stripe technology) or a direct line of sight to a reader (as does bar code technology). RFID, therefore, reduces the problems associated with those “contact” or “line-of-sight” technologies. This means RFID can operate in harsh environments and is not usually affected by temperature changes, except under extreme conditions.
The RFID System Components
An RFID system is comprised of several components including:
- Tags: This is sometimes referred to as a transponder.
- Readers: This is sometimes referred to as an interrogator.
- Antennas: Linear or Circular polarized.
- Software: This may also be referred as middleware.
Antenna: The antenna emits radio signals to activate the tag and read and write data to it. Antennas are available in a variety of shapes and sizes; they can be built into a doorframe to receive tag data from persons or things passing through the door, or mounted on an interstate tollbooth to monitor traffic passing by on a freeway. Antennas can also be mounted on mobile devices and under print heads.
Transceiver: Often the antenna is packaged with the transceiver and decoder to become a reader (a.k.a. interrogator), which can be configured either as a handheld or a fixed-mount device. The reader emits radio waves in ranges of anywhere from one inch to 100 feet or more, depending upon its power output and the radio frequency used. When an RFID tag passes through the electromagnetic zone, it detects the reader’s activation signal. The reader decodes the data encoded in the tag’s integrated circuit (silicon chip) and the data is passed to the host computer for processing.
RF Tags or Transponders: RFID tags or transponders come in a wide variety of shapes and sizes. Animal tracking tags, inserted beneath the skin, can be as small as a pencil lead in diameter and one-half inch in length. Tags can be screw-shaped to identify trees or wooden items, or credit card-shaped for use in access applications. The anti-theft hard plastic tags are attached to merchandise in stores. Small tags can be placed on wooden pallets, totes, or other containers to track their movement or read and verify their contents. In addition, heavy-duty transponders are used to track containers or heavy machinery, trucks, and railroad cars.
Tags: There are a variety of RFID tag types. Selecting the correct tag will be imperative to ensure a proper functioning system. Selecting the proper tag will be discussed later. Tags can be placed on wooden or plastic pallets, clothing, embedded into traditional barcode labels, animals, metal surfaces, and much more.
A tag is comprised of:
- Silicon chip: Integrated circuit (IC chip) that contains the data.
- Antenna: An antenna is attached to the chip in order to receive and transmit its data.
- Substrate: This is the paper or plastic film or housing that the chip and antenna are mounted on.
The data associated with a tag is programmed into the chip. The tag is placed on merchandise and is activated and read when it is energized by the reader and antenna system.
The IC contains an actual microchip where data is stored. Chips are available in many sizes and configurations. They can be extremely small to be incorporated into small form factor RFID tags. The chips’ capability to carry data and have that data amended is defined by their Read/Write characteristics.
An RFID tag can take on many form factors and power levels. The unique identifier is encoded onto the integrated circuit and travels with this data. The data on the RFID IC is transmitted to a reader through the antenna incorporated onto the tag. RFID tags can be as tiny as an ant’s head, larger than the palm of an adult hand, or any size in between. The form factor that the RFID tag takes is dictated by factors including power, durability, and lifetime requirements. Tag characteristics are defined by the application, and can vary in power requirements, read/write capability, and frequency. RFID tags are developed using a frequency according to the needs of the system including read range and the environment in which the tag will be read.
Types of RFID Tags
There are two basics types of tags: Passive Tags and Active Tags
Passive Tags: “Passive Tags” are RFID tags that have no independent power source and get power from the readertransceiver directly.
Passive tags are consequently much lighter than active tags, less expensive, and offer a virtually unlimited operational lifetime. The trade off is that they have shorter read ranges than active tags and require a higher-powered reader. Passive tags will be the most common tags associated with merchandise tracking.
Read-only tags are typically passive and are programmed with a unique set of data (usually 32 to 128 bits) that cannot be modified. Read-only tags most often operate as a license plate into a database, in the same way as linear barcodes reference a database containing modifiable product-specific information.
Active Tags: Active tags are powered by an internal battery and are typically read/write, i.e., tag data can be rewritten and/or modified. An active tag’s memory size varies according to application requirements. The battery-supplied power of an active tag generally gives it a longer read range. The trade off is greater size, greater cost, and a limited operational life, depending upon operating temperatures and battery type.
Semi-Active tags incorporate batteries, but the battery power is only used to power the IC’s circuitry, not to enhance communications with the host system reader. These tags are less common, but are an emerging solution that combines the longer read ranges of active tags with the lower cost of passive tags.
Reading and Writing RFID Tags
RFID tags can be either read write (R/W) or read only (R/O), or some combination of these. Read Write tags allow data to be updated or written to the RF Tag. These tags would be needed, for example, when a history of movement is needed. Read Only tags are used when only the static content of the tag is needed.
Read Only: Read Only tags contain identification such as a product or serial number that is programmed onto the chip when it is manufactured. This identifier remains constant throughout the chip’s life; neither additional data nor overwriting the identifier is possible. Read Only chips are generally the least expensive but have the limitation of acting like a license plate, much like a bar code acts.
Write Once Read Many (WORM): A Write Once Read Many (WORM) chip allows users to add data onto the chip beyond the unique identifier, but data can be added only once. There is no limit to how many times the data can be read.
ReadWrite: ReadWrite chips are open to data manipulation by the user’s system without restrictions. These chips will still contain a unique identifier from the chip manufacturer, but can also carry an updateable database where data can be added to the chip. ReadWrite chips are generally more expensive than read only or WORM chips because of their versatility.
Additional notes: Passive tags are the least expensive of all the current tag types. Passive tags are activated by the electromagnetic waves of a reader. These waves effectively “turn the tag on,” allowing it to transmit radio frequency waves with specific information. Passive tags will be the first to see widespread adoption because of their low cost. These tags will have a limited read range of 10-25 feet depending on environmental conditions, mounting surfaces, and method of use (ie: speed of desired read).
Active tags, on the other hand, contain a battery that allows them to constantly emit radio frequency signals that can be picked up from 100 feet or more away. These are useful for larger objects because they don’t require as many readers. While having a power source provides various benefits, including reducing the impact of metals and liquids, active tags are significantly more costly than passive tags.
Another determination for companies to make is whether to invest in read-write tags or read-only tags. Read-write tags are significantly more expensive, but allow users to add or write over existing information. Read-only tags are much less expensive, but are good for one time recording of information only. With a variety of tag options to choose from, the selection of the tag will be determined by the way the tags will be used and the application they are associated with. For example, if a company needs to more closely monitor its yard, attaching a higher priced active tag to a trailer or container of product would allow for instant location in a large area. However, if a company just needs to automate its picking processes within the DC, it would likely choose to invest in passive technology.
Bottom Line: TPI can help improve your business through RFID technology.