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What is RFID?
Radio Frequency Identification (RFID) is an advanced identification technology. It uses radio-frequency waves to identify, detect, track and sort variety of objects including people, garments, pallets, containers and vehicles. It can be used in applications such as

Proximity access control, time-and-attendance management, vehicle identification, laundry/textile identification, asset tracking, inventory control and factory automation.

RFID relies on radio frequency or "waves" between a card or tag and a reader in order to

make an identification. Because RFID is a "contactless" technology, it requires neither

contact with a reader 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. For instance, a "good" read can occur through sunlight, wet, cold (-30°C ), frost, dirt, grease, and many corrosive chemicals.

How Does RFID Work?
An RFID system consists of components--the Reader, the antenna and the card/tag. They work together to provide the end user with a non-contact solution to uniquely identify people, animals or objects.

The reader performs several functions, one of which is to produce a low-level radio frequency magnetic field. The RF magnetic field emanates from the reader by means of a transmitting antenna, typically in the form of a coil. The magnetic field serves as a "carrier" of power from the reader to the RFID card or tag.

The RFID card or tag contains an antenna, also in the form of a coil and an integrated circuit (IC). The IC requires a small amount of electrical power in order to function. The antenna in the tag provides a means for gathering the energy present in the magnetic field produced by the reader and converts it to an electrical form of energy for use by the IC. When a card or tag is brought into the magnetic field produced by the reader, the converted energy powers the IC. This enables the transmission of the IC's memory contents in the form of an electromagnetic signal to the reader via the tag's antenna.

The tag information is received by an antenna within the reader and converted back into an electrical form. The reader contains a sensitive receiving system that is designed to detect and process the tag signal. Once the tag data has been processed, a microcomputer within the reader checks to verify that the signal received is valid.

Once the reader has checked and validated the received data, the data is then decoded and restructured for transmission to the end-user's host computer. This restructuring provides the data in both an electrical form and a protocol (or format) that is required by the host computer system. Once the restructuring process is complete, the data is transmitted to the host system.

RFID Tag:
RFID Tag consists of a microchip attached to an antenna that is packaged in a way that can be applied to an object.

The tag picks up signals from and sends signals to a reader. The tag contains a unique serial number, but may have memory to store applicable information also. RFID Tag can be Active or Passive depending on the application requirement.

Antenna:
The microchip antenna is the conductive element that enables the microchip to send and receive data. Readers also have antennas which are used to emit and receive radio waves.

Reader:
This is the device used to communicate with RFID microchips. The reader has one or more antennas, which emit radio waves and receive signals back from the tags. The reader is also called as interrogator because it “interrogates” the signals from the microchip. The reader is equipped with appropriate software to transform raw data into actionable information.

Benefits of RFID
RFID benefits the user similarly to other automatic identification technologies in that it

reduces the need to collect data by cumbersome means like paper and pencil. Often the amount of data to be collected is so overwhelming and the time needed to process the information is so long that the only practical method of collecting the data is automatically with computer technology.

Automatic data acquisition improves the value of the information in a system by making the information available sooner. In a manufacturing facility the value of finding out that work in process has been misrouted is valuable if discovered quickly. Unlike the barcode, RFID enable the auto identification of items, without the need to place the barcode label in front of the reader. RFID solves this problem by wirelessly transmitting the identification information of the items to the reader. No line of sight is required.

Operating frequency is the determining factor for the type of application an RFID system is best suited for. These frequencies include high frequency (850-950 MHz and 2.4-5 GHz), intermediate frequency (10-15 MHz) and low frequency (100-500 KHz).

High-frequency

RFID systems are suitable for applications requiring a longer read range such as supply chain, inventory, assembly lines, toll-collection systems and railroad car and intermodal container tracking.

Intermediate-frequency

RFID systems are just now beginning to emerge in the financial transaction processing areas of smart card use.

Low-frequency

RFID systems are used for applications requiring shorter read ranges. These include access control, work in process tracking and asset management. As you move up in frequency, you not only receive an increase in passive read range but also an increase in the speed at which the device can operate. Longer range tags in the hundreds of MHz and GHz are measured in yards and miles. Lower frequency tags in the

125 kHz and 13.56 MHz range have read ranges measured in inches and feet. Application requirements for minimum read range, cost ceilings, speed of operation and communications complexity drive the decision as to which frequencies to deploy.

RFID Characteristics
There are six key characteristics of RFID that affect the communication between a tag and reader: Range, Range Adjustment, Propagation, Directionality, Multi-Tag Collection and Memory.

Range
Range is defined as the maximum distance for successful Tag-Reader communication. Read range difference will vary and can be very-short, short, or long.

Range Adjustment
Range Adjustment will also play a role in RFID tag read functionality. Range adjustment is the ability to adjust range and is categorized as very good or poor. Very good range adjustment can be fine-tuned to a specific distance. Tag-Reader communication is guaranteed within the specified range and tag-reader communication outside the range is impossible. Whereas poor range adjustment cannot be adjusted well at all. When there is a signal fall-off pattern or a reflection, tag-reader communication in the physical area is not guaranteed.

Propagation
Propagation is the ability to perform tag-reader communication through or around objects and material. With very good propagation, the radio frequency can penetrate through objects allowing successful communication between tag and reader. Plus, very good propagation allows for penetration through water, liquids and human tissue and may even go through metal. Whereas poor propagation works on in line-of-sight and any obstacle such as a wall, people or vehicles between the tag and reader will prevent any successful communication.

Directionality
Directionality is the ability to achieve directional RF coverage using directional antennas. There are two types of directionality: Omni-directional and Directional. Omni-directional coverage has similar RF coverage in all directions. With directional coverage, the RF coverage is much stronger in one specific direction.

Multi-tag collection
Multi-tag collection is the ability to quickly and reliably collect large number of tags within a designated area.

Memory
Memory is key in RFID communication — it determines the read only, read/write, or write once read many capabilities in the tag-reader communication. Some tags have small memory size at 16 bits and others have larger memory with 512 KBytes or more.

Active vs. Passive Technology
RFID tags are categorized as either active or passive. Active RFID tags typically have both read and write capabilities so tag data can be rewritten and/or modified. Active RFID tags can transmit specific data or instructions to a reader (where the tag has been or important information about the items in the container). A passive tag can not actively send information — it is read only. Plus, active tags are powered by an internal battery which gives them a longer read range.

Passive RFID tags operate without a separate external power source and obtain operating power generated from the reader. They have shorter read ranges than active tags and require a higher-powered reader. Read-only tags are typically passive and are programmed with a unique set of data (usually 32 to 128 bits) that cannot be modified. Passive tags are lighter, have smaller form factors and are less expensive then the more powerful active tags.

Active and Passive RFID are two fundamentally different technologies, each with unique advantages. While often considered competing technologies, they actually complement each other, balancing cost and capability. Active and Passive RFID offer tremendous potential for combined use within many applications, including air cargo and intermodal cargo management. Along with technical performance and regulatory issues, this opportunity for combined use must also be considered when selecting a frequency for Active RFID.

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