RFID Primer: Where the WLAN Hits the RFID Fan

By Alex Goldman

December 23, 2003

RFID, the technology that places data on small tags to be read by computers attached to antennas, is widely feared and misunderstood. We break open the myths, starting with a few simple facts.

Introduction

Headquartered in Atlanta, Georgia, Tech Center is a VAR and Systems Integration firm specializing in custom software solutions, WLAN designs and Security, Auto ID (Bar Code and RFID) and VoIP (Cisco) telephony technologies. The company does front-end and back-end systems, from wireless data collection at the edge back to the ERP and CRM databases that major corporations use to track their assets and performance.

Working as a Certified RFID Honors Partner with Intermec, a pioneer in the RFID space, with large clients including major Automotive companies, Tech Center plays a significant role in this emerging market. The company already has several RFID implementations to their credit, something few other VARs can lay claim to.

RFID theory

An RFID tag is based on a chip or integrated circuit (IC).

A tag insert or inlay is the IC attached to an antenna, which is usually printed or etched on a substrate material.

The tag itself is the inlay plus its encapsulated protective packaging. The packaging can be flexible or stiff, as the application warrants.

An RFID system typically consists of a radio-enabled device that communicates with or "interrogates" a tag or label, which is embedded with a single chip processor and an antenna.

The "interrogator" or RFID reader may be a fixed antenna or it may be portable, like a bar code scanner. The tag itself is an extension of the bar code labels you see everywhere today, but with more intelligence. The advantage of these more intelligent systems is that, unlike barcode tracking systems, an RFID system can read the information on a tag without requiring line of sight or a particular orientation. This means that RFID systems can be largely automated, reducing the need for manual scanning.

In the back end of the system, a host computer stores all collected data within a database. Since RFID tags can also carry data, tags can serve as data transfer agents, synchronizing disparate information systems. Tags may carry a product's history or genealogy, and may interact and communicate with manufacturing production systems for increased automation and process error proofing.

Tag types and tag selection

When selecting a tag or insert, you must first consider the general performance characteristics and the regulatory requirements associated with the permitted frequencies for your country of operation.

There are two types of RFID tag: active and passive.

Active

  • Battery powered
  • Read-write and read only versions available
  • Longer read ranges (25 to 100 feet)
  • Higher tag costs ($20 to $70 per tag)
  • 2D location systems possible
  • Example: toll booths

Passive

  • Powered by reader
  • Read-write and read only versions available
  • Shorter read ranges (Inches to 20 feet)
  • Lower tag costs (at least $1 per tag)
  • Item ID
  • Example: item management

RFID deployments tend to use unlicensed frequencies for their obvious cost benefits. There are four commonly used frequencies: low frequency (LF) 125/134.2 KHz, high frequency (HF) 13.56 MHz, ultra high frequency (UHF) (including 869 and 915 MHz) and microwave (at 2450 MHz, a band familiar to ISPs).

A tag's read range performance is usually considered the primary gauge of its suitability for a particular application. It is important to remember that not all applications require maximum range.

Tags in the LF-HF band have a range of 1 to 18 inches, while passive UHF tags can reach up to 20 feet, and microwave tags can reach 1 to 6 feet. The ranges greatly depend upon the surface on which the tag is mounted.

Each tag can be "tuned" to work with the material it is mounted on, whether metal, glass, plastic, wood, or air. If you take a tag designed for a glass windshield at 915 MHz, and attach it to a wooden pallet, you may not be able to read it. Any experienced RF user will know that each frequency requires a slightly different antenna shape.

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