RFID Primer: Where the WLAN Hits the RFID Fan


Headquartered in Atlanta, Georgia, Tech
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.


  • 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


  • 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.

Tag complexities

All RFID tags are not the same! Tag capabilities and performance vary widely
amongst the different brands and makers. Intermec currently makes dozens of
different RFID tag designs based on the same IC chip, and that number should
increase as new applications emerge. That’s because tags are designed and tuned
for particular target items, environments, and mounting materials, with each
presenting different challenges to the tag designer.

Each vendor’s IC chip functions also vary greatly. Temperature ratings,
radiation tolerance, arbitration (handling data collisions), simultaneous
multiple tag reads and read rates, reading groups of tags (group select),
reading only particular tags (item search), are vendor specific features and

Since RFID is RF technology, many of the same principle issues apply.

Any experienced RF user will know that each frequency requires a slightly
different antenna shape.

Tags mounted on metal require an “air gap” between the tag and the item to
which the tag is attached. If the size of the air gap changes (for example, if
the metal bends), the tag will be detuned.

And, of course, there are interference issues, as with any RF application.
Each tag antenna has a magnetic field. If its field overlaps with that of another
tag, readings can be subjected to interference, and whole tags can be hidden.
For example, a jeweler who wanted to tag every ring on a jewelry counter would
find that the tags were too close together.

RFID readers and interrogators

Tags transmit data to readers or interrogators. They can be fixed mounts, handheld,
or PCMCIA cards (at this time, only Intermec makes a PCMCIA card reader).

Each reader can have several antennas. For example, a fixed reader on a
factory’s conveyor belt might need only one antenna but a fixed reader on the
same factory’s massive doors might need several. Linear polarization is usually
appropriate for applications such as conveyor belts where both antenna and tag
will be aligned in a fixed manner. PCMCIA card readers can be used to enable
RFID data collection in places where the other two options would not work. For
example, Tech Center has used the card to enable data collection on computers
mounted on forklifts (more on this later).

For handheld readers, circular polarization is usually appropriate. People
are accustomed to lining up infrared readers with barcode tags, but they can see
the infrared whereas they cannot see RF. Since RF is invisible, its alignment
cannot be eyeballed.

Handheld interrogators typically have only one antenna, and can use linear or
circular polarization. A handheld typically performs at 60 percent to 70 percent
shorter ranges than a fixed mount, and writing to a tag can also reduce range by
70 percent. For example, the maximum read distance for a fixed antenna operating
in the 915 MHz band is 20 feet. Its write distance is about 14 feet. A handheld
using the same frequency band could read at about 15 feet and write at about 9

Tech Center usually customizes the reader and antenna design for a particular
application. This includes design consideration for connecting the RFID
subsystem to the client’s network and backend systems. Switches, hubs, network
traffic, port redirection software, client and network security, etc. are all
important considerations in a successful RFID subsystem design and

Intermec has designed a handheld interrogator, the IP3, incorporating the
company’s Model 750 mobile computer based on the PocketPC OS, and a custom
plastic handle containing a circular polarized antenna. It complements the
Intermec. Sabre. 1555 linear polarized antenna that handles both RFID and
infrared (for bar codes). These units provide Tech Center and other VARs a
diverse set of tools for tethered and portable RFID system designs.

No stranger to customization, Tech Center designed a tether less 2D Bar Code
imager for a major automotive client by adding a radio/camera battery package to
an Intermec 1470B imager. “The Blob” allows Datamatrix codes to be read on tires
and aids efficiency by allowing worker mobility.

For a warehouse application, Tech Center customized a forklift-mounted
computer, turning it into what the company calls its “TC Smart-Lift.” For OSHA safety
considerations, the reader had to be inoperable while the forklift was in
motion, so Tech Center designed patent-pending technology that blanks the screen
whenever the forklift’s transmission is not in Neutral. Smart-Lift antenna array
designs for pallets and large cartons are also ready for supply chain readiness


Printers have been available for a long time for bar codes and for printed
labels, but they are quite new in the RFID space. RFID printers are standard
bar code printers with an RFID interrogator, enabling the printer to program
the embedded chip and print a label.

Human readable labels, both with and without bar codes, are found on all
kinds of products and items in the supply chain. Adding a RFID tag inlay behind
the label to carry product ID and other data will prove to be a leading
application for RFID technology.

Already this concept has been named the “smart label”. Recent RFID supply
chain compliance mandates will escalate the use of RFID “smart labels”. “Smart
labels” may be printed and coded simultaneously by the latest generation of RFID
enabled printer/tag writers.

Both Intermec and Zebra now offer devices capable of this function in
anticipation of significant future demand for this RFID application.


RFID has all of the security problems posed by traditional WLANs. Deployments
face the same issues with security protocols, the need to rotate passwords frequently
(especially in large rollouts where many people know the same password), and
other problems familiar to wireless network administrators.

To solve most of these problems (technology cannot prevent human error), Tech
Center has developed the TC-Brick network security appliance, a hardened Client
Bridge that automatically rotates WEP keys via Wavelink Avalanche client
software and connects Ethernet and RS 232 devices to the WLAN.

As RFID deployments grow in size and complexity, the security hardware and
software they require will grow in tandem.

You need a partner

Tech Center has noted, with some alarm, that some companies are selling RFID
vendor development kits. Given the complexities outlined above, any RFID implementation
rolled out by a novice is doomed.

At this moment, the industry consists of the following companies:

4 major chip technology providers: Philips, Texas Instruments, EM
Microelectronic-Marin SA, and Impinj, plus several smaller players.

Over 35 major tag providers including Intermec, Texas Instruments, RafSec,
KSW-Microtec, Hana, BiStar, and others.

Over 15 universal reader/interrogator vendors including Intermec, Texas
Instruments, Philips, Sharp, Transcore, Samsys, AWID, Matrics, Alien
Technologies, and others.

But there are very few experienced solutions providers. Global consulting
companies like IBM Global Services and Cap Gemini Ernst & Young compete in
this space.

Companies like Tech Center that have real hands on experience and actual
implementations in RFID, Bar Code, WLAN, WMS, MES, ERP, CRM and custom software
integration are today’s answer and assurance to the successful, on time and
within budget, RFID rollout.

RFID opportunities will certainly grow, but the opportunities and their import
are widely misunderstood. That’s the subject of a future article, “Five RFID
Myths Exposed.”


Reprinted from ISP Planet.

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