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Examining the Elements of a Basic RFID System

Learning the fundamentals of RFID can be overwhelming. By understanding the basics of how data travels in waves and then through a network in an RFID system, however, you gain a solid foundation for greater knowledge as you explore the global architecture of RFID.

In a basic RFID system, four fundamental components are required for data to make its grand journey:

  • A transponder (more commonly just called a tag) that is programmed with information that uniquely identifies itself, thus the concept of "automatic identification"
  • A transceiver (more commonly called a reader) to handle radio communication through the antennas and pass tag information to the outside world
  • An antenna attached to the reader to communicate with transponders
  • A reader interface layer, or middleware, which compresses thousands of tag signals into a single identification and also acts as a conduit between the RFID hardware elements to the client's application software systems, such as inventory, accounts receivable, shipping, logistics, and so on

Here's an overview of how a passive RFID system works:

1. The tag is activated when it passes through a radio frequency field, which has been generated by an antenna and reader.

2. The tag sends out a programmed response.

3. The antenna that generated the field originally and is attached to the reader detects that response.

4. The transceiver (or reader) sends the data to the middleware.

5. The middleware sends the information contained in the tags to whatever systems need that information.

Everything starts with the tag

A tag, in a passive RFID system, is a little transceiver waiting to be turned on (and no, that doesn't happen by seeing a tag of the opposite sex). The tag has a small computer chip (or memory area) that is programmed with information that uniquely identifies the tag. This information is sent when the tag is activated (turned on).

A passive RFID transponder does not contain its own power source; rather, it absorbs energy propagated from a reader antenna's radio frequency (RF) field to supply all the power it needs to wake up its chip and communicate with a reader by sending back (backscattering) the information contained in its memory to a receiving antenna. As tags move into an antenna's radio field, they are excited, and each one transmits its identification data.

Antennas send and receive radio waves

Both tags and readers have their own antennas because they are both radio devices. A tag antenna, which is only a few centimeters (or less) long, attaches to the integrated circuit (IC, or just chip) to absorb a signal and then transmit out a slightly modified signal. The reader antennas range in size but are generally about the size of a computer flat screen and are specially tuned to transmit and receive RF signals.

Antennas are how readers communicate with the outside world. Reader antennas send radio signals into the air to activate a tag, listen for an echo (or backscatter) from the tag, read the data transmitted by a tag, and, in some cases, write data onto a tag. Antennas act as conduits between the tag and the transceiver and can function continuously or on demand.

  • Continuously active antenna systems are used when tagged items are present on a regular basis or when multiple tags are passing through the antenna's detection field.
  • On the other hand, an antenna's detection field can be activated only when needed by a sensor of some kind. The on-demand method can be triggered by optical, pressure, or other kinds of proximity sensors.

Antennas come in a variety of shapes and sizes; this diversity in size and shape allows antenna placement in a wide variety of locations — from warehouse doors to highway tollbooths.

Readers tell the antennas what to do

An antenna is connected to a transceiver (which is generally known as a reader). Typically, one to four antennas are attached to a single reader, and those antennas send out the reader's signals. Basically, the reader tells the antennas how to generate the proper RF field, which can cover an area as small as 1 inch to as large as 100 feet or more, depending on the power output and the frequency. When an RFID transponder (or tag) moves into the antenna's radio field, it becomes active and sends back to the antenna whatever information has been programmed into its memory. A reader receives the tag's signal through its array of antennas, decodes the signal, and sends the information to the host computer system. A reader can also transmit special signals to a tag — telling a tag to come alive, synchronizing a tag with the reader, or interrogating all or part of the tag's contents.

The middleware transforms the system into a network of objects

The basic elements of an RFID system are rarely useful in isolation. They gain value as part of a production or logistics system. In this way, the use of more than one system in an industrial process becomes a local network. The connection of local networks constitutes a global network. You can think of the local networks as a node of hardware (a reader, antennas, and tags) that interacts within itself to exchange information over RF waves. A bunch of nodes connected together creates a global network that connects to an application that creates useful information out of the data.

In order to move data from a single node to the local network and/or to the global network, you need the data-collection component, which ties readers, antennas, and tags together. This component is called by many names — middleware, reader interface layer, Savant — all describing the very simple glue that sticks together each node in an RFID system.

Middleware connects the data coming into a reader to the client's host software systems. The middleware provides a coherent and stable interface between the RFID hardware operations and the flow of data elements, such as EPC (electronic product code) numbers, into inventory, sales, purchasing, marketing, and similar database systems distributed throughout an enterprise.

The elements of middleware include the following:

  • Reader and device management: RFID middleware allows users to configure, monitor, deploy, and issue commands directly to readers through a common interface.
  • Data management: As RFID middleware captures EPC data or other data from readers, it can intelligently filter and route it to the appropriate destinations.
  • Application integration: RFID middleware solutions provide messaging, routing, and connectivity features required to integrate RFID data into existing supply-chain management (SCM), enterprise resource planning (ERP), warehouse management (WMS), or customer relationship management (CRM) systems.
  • Partner integration: Middleware can provide collaborative solutions like business-to-business (B2B) integration between trading partners.

The basic elements provide the data source or the local node to generate data. A series of these are linked into a local network that can connect to either a larger network or even a global network by employing middleware. An RFID network is a peer-to-peer architecture capable of aggregating highly actionable data to a central location.

Imagine this: The use of a single tag, no larger than a book of matches, is multiplied millions of times over within a global supply chain, which creates a peer-to-peer network that shares data in real time across a limitless number of boundaries. The image of the single millimeter-sized chip quickly expands to comprise a warehouse; a company; an industry; and a world of rapidly changing, automatically updated, real-time information. From that tiny chip blossoms the power to know where every object is at all times in a global network. Pretty cool, huh?

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