How does RFID work?

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RFID belongs to a group of technologies referred to as Automatic Identification and Data Capture (AIDC). AIDC methods automatically identify objects, collect data about them, and enter those data directly into computer systems with little or no human intervention.

RFID methods utilize radio waves to accomplish this. At a simple level, RFID systems consist of three components: an RFID tag or smart label, an RFID reader, and an antenna. RFID tags contain an integrated circuit and an antenna, which are used to transmit data to the RFID reader (also called an interrogator). The reader then converts the radio waves to a more usable form of data. Information collected from the tags is then transferred through a communications interface to a host computer system, where the data can be stored in a database and analyzed at a later time.

Tag Antennas

Tag antennas collect energy and channel it to the chip to turn it on. Generally, the larger the tag antenna's area, the more energy it will be able to collect and channel toward the tag chip, and the further read range the tag will have.

There is no perfect tag for all applications. It is the application that defines the tag’s antenna specifications. Some tags might be optimized for a particular frequency band, while others might be tuned for good performance when attached to materials that may not normally work well for wireless communication (certain liquids and metals, for example). Antennas can be made from a variety of materials; they can be printed, etched, or stamped with conductive ink, or even vapor deposited onto labels.

Connectivity Devices Identify, Locate, Authenticate, and Engage Endpoints

RAIN RFID readers and gateways are devices that power and communicate wirelessly with tags and deliver tag data to operating-system software. Connectivity devices communicate bi-directionally with endpoints that are within their field of operation, performing any number of tasks including simple continuous inventorying, filtering (searching for tags that meet certain criteria), writing (or encoding) selected tags, etc.

Connectivity devices can identify and locate more than 1,000 items per second. Readers can be stationary or mobile and use an attached antenna to capture data from tags. Gateways integrate stationary readers with scanning antennas to locate and track tagged items. Reader chips and modules are designed for to be embedded in applications like handheld readers, smart vending machines, automotive tracking, mobile devices and more.

Stationary readers require an antenna that sends power, as well as data and commands to endpoints. Since these readers are often used in automated applications they can support additional connections to external presentation sensors or light stacks to notify users of completed reads. Readers and gateways are connected to a host PC or network to transmit all of the tag data.

Reader Antennas

RAIN RFID readers and reader antennas work together to read tags. Reader antennas convert electrical current into electromagnetic waves that are then radiated into space where they can be received by a tag antenna and converted back to electrical current. Just like tag antennas, there is a large variety of reader antennas and optimal antenna selection varies per the solution's specific application and environment.

The two most common antenna types are linear- and circular-polarized antennas. Antennas that radiate linear electric fields have long ranges and high levels of power that enable their signals to penetrate through different materials to read tags. Linear antennas are sensitive to tag orientation; depending on the tag angle or placement, linear antennas can have a difficult time reading tags.

Choice of antenna is also determined by the distance between the RAIN RFID reader and the tags that it needs to read. This distance is called read range. Reader antennas operate in either a "near-field" (short range) or "far-field" (long range). In near-field applications, the read range is less than 30 cm and the antenna uses magnetic coupling so the reader and tag can transfer power. In near-field systems, the readability of the tags is not affected by the presence of dielectrics, such as water or metal, in the field.

In far-field applications, the range between the tag and reader is greater than 30 cm—and in fact can be up to several tens of meters. Far-field antennas utilize electromagnetic coupling and dielectrics can weaken communication between the reader and tags.

Last update: Apr 24, 2018


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