Radio Frequency Identification, or RFID, is a technology which can be used in a wide variety of businesses and industries. A prominent use of this technology is in logistics, but applications are widespread and growing in healthcare, security, and agriculture. These RFID systems prevent theft in stores, track shipping containers and railcars; golfers can even improve their game with club and wrist-mounted RFID systems. A popular consumer use is to provide security to credit cards through imbedded RFID chips.

RFID systems include one or more interrogator/readers, physical antenna portal structure, associated RFID tags, and data processing support. The interrogator/reader both powers the RFID tag chip and extracts its data. These are often embedded in door portals, production machinery, or mobile scanners. The tag is a microchip which is connected to a small antenna. The whole thing covered in plastic may be as small as a rice grain, or it may be printed with conductive materials on credit cards or labels.

Configuration of a basic RFID system

Configuration of a basic RFID system

How does the technology work?

In principle the steps of RFID system operation are straightforward:

• A radio signal gets sent by the interrogator device

• The RFID tag rceives it

• If a passive tag, which the vast majority are, part of the received RF power is diverted to energize and operate the tag, while the remainder is decoded and used by the tag processor as data/instructions

• Using the recovered RF energy to power its transmitter, the tag then responds with an ID code and data load

Because the available RF power at the tag is very small, tags and reader antennas must generally be close together. Depending upon frequency and coupling technology, distances of inches to a few feet are the maximum. For longer distances, active tags are used which incorporate a battery, and do not rely on the reader for RF power.

Basic circuitry of a simple inductive interrogator and tag

Basic circuitry of a simple inductive interrogator and tag

The vast number of applications demands a wide array of antenna configurations to enable the coupling of interrogator/reader and the RFID tag. Most familiar are the anti-theft portals in retail stores, scanner “guns”, and flat scanners for credit cards on ATM’s, gas pumps, and more.

RFID readers assume a wide variety of configurations

RFID readers assume a wide variety of configurations

Reader antennas may be deployed in different ways. Here are just a few:

· Built directly into walls

· Installed on forklifts

· Incorporated into production lines

In many of these installations, RFID system performance is mission critical. Often the reader antennas may not be visible, may be subject to mechanical damage or may become obstructed in ways that hinder their performance. Many of these applications can be extremely challenging to designers and maintenance forces.

Most RFID applications employ multiple readers which must be appropriately networked to realize the system objective. Where RF networking is used, such as WiFi or WLAN, care must be taken that the networking devices do not adversely affect the RFID system.

A significant consideration in RFID deployment is low level RFID signal protection from RF interference and limiting signal access to appropriate users and devices.

Detailed discussion of RFID system theory is beyond the scope of this overview, but the paper at http://polygait.calpoly.edu/ is recommended for further study.

Let us check out some typical uses of RFID technology:

· In retail stores: Radio Frequency Identification is often used in clothing and other merchandise stores. The shop owners put tags on each item before it is arranged on shelves. When a customer buys an item, the clerk removes or disables the RFID tag. If an active tag passes by the exit of the shop, the alarm rings and the shop owners can detect attempted shoplifting. At the same time, RFID tags can help identify and inventory delivered goods from suppliers. The tags don’t cost much, but they are extremely helpful in managing and safeguarding retail goods.

· For access control: Identification cards often make use of RFID technology. The cards can not only automatically open doors to restricted rooms or other areas, but provide logging information about the accessing party as part of an electronic access system. In the automobile industry RFID can automatically unlock the door when the driver approaches, or provide validation to start the engine. The need for age-old keys is being eliminated by RFID.

· In healthcare managemnt: Asset tracking in hospitals is a vital aspect in improving costs and services. RFID technology is helping hospitals to efficiently track medical carts, crash carts and other assets. Pharmaceuticals and patient supplies can be RFID tracked for security, billing, and logistics. An enormous amount of manual labor and record keeping can be saved by using this technology. Hospital personnel can locate assets of varying levels of importance. Tagging and tracking helps hospital personnel to know what they have and what they do not have or what they need to replace.

· For animal management: Veterinarians can put RFID tag on farm animals for many tracking purposes. Tags can help in locating agricultural animals in case of loss or theft. In addition to tracking, the RFID system can do a variety of other sophisticated tasks like recording growth history, milk production, and origin.

A complex RFID nuclear waste tracking system by Argonne National Labs

A complex RFID nuclear waste tracking system by Argonne National Labs

· For weaponry and dangerous goods: Keeping explosives, sophisticated weapons, and hazardous waste safe and accounted for is a daunting task. For the military and police forces. RFID medical carts allows such items as evidentiary weapons, military arsenals, and explosive cache materials to be tagged and tracked. For instance, RFID readers and sensors can be added to weapons racks in order to monitor the access to assets. RFID systems are typically very low power and safe for use in explosive environments. Alerts can notify guards about the removal of weapons. Control of hazardous wastes is another vital use. Dangerous assets can be located and their movement continuously tracked. This is an application where active RFID tags are often used, some so powerful that they can be interrogated through satellites.

· Transportation logistics: RFID systems, both active and passive, are becoming widely used in all modes of freight transportation. Roadside and track side readers interrogate rail cars and freight trucks to track goods manifests and safety information. Satellite RFID readers even track cargo containers on the high seas. Tracking tags also permit warehouses to use very sophisticated robotic goods pickers to stack and retrieve inventory, and track stock levels. In a typical roadside use, advance reading and approval of RFID information at roadside weigh stations permits cleared truckers to avoid stops at these facilities, saving trucker time and transport inspector resources.

System considerations in using RFID Technology

Several technical aspects of RFID need to be considered in evaluating, fielding, or using a system. Because RFID transceivers are generally very low power, they are susceptible to a wide range of interference issues, both internal to the system and external. In many cases, the material upon which a tag is mounted is critical to performance, and separations between tags and transponder may be critical.

Typical frequency spectrum available for RFID

Typical frequency spectrum available for RFID

· Spectrum considerations: Most RFID systems operate in frequency bands which are generally, but not always, license-free internationally. Typically, unlicensed frequencies are around 134 kHz, 13, 900, and 2400 MHz. Active tags often use frequencies in the 400 MHz area, along with garage door openers and automobile key fobs. The passive tag frequencies are shared with all manner of intentional and unintentional RF radiators including industrial welding systems, WiFi, microwave ovens, and much more.

· System design issues: Simple RFID systems intended as card readers and the like are pretty much out of the box, plug and play. However, systems used for inventory control, automatic picking, loading dock applications, and cargo tracking are much more complex. They also are often mission critical and must be performance verified and not susceptible to interference or other disruption. When used in industrial environments, mechanical abuse and contaminant buildup may be serious performance compromisers. These systems are often networked, and the choice of interconnection technology can be critical.

Congested frequencies near 900 MHz RFID spectrum show potential for interference

Congested frequencies near 900 MHz RFID spectrum show potential for interference

· Interference issues: Since most RFID operates in unlicensed frequency bands, it is not protected from interference by RF regulatory authorities. The responsibility for implementing and maintaining an interference-free RFID system is entirely upon the user. That means a complete characterization of the operational site for presence of potential interferers. Once that is known, appropriate avoidance strategies may be implemented. These may include:

1- Best frequency technology selection

2- Strategic positioning of RFID and interferers in the facility

3- Electromagnetic shielding of RFID installations, interferers, or both

Each locality presents a different set of considerations.

· Radio frequency safety: RF energy has the potential to do both human and system harm. Fortunately, power levels in most RFID systems are far too low to present fields which could exceed RF safety regulatory limits in most countries. However, these effects should be evaluated where high power active systems are being considered. If hazard potential is found, then appropriate safety measures should be instituted which may include signage, shielding, personnel RF safety training, and the use of personal RF monitors.

Examples of deployment challenges

LBA has dealt with a variety of RFID problems, a couple of which may be illustrative of how adequate planning could have avoided the pitfalls. Here are some of the case studies:

· The case of the screaming baby monitor – A US hospital had newly installed a baby security monitor in its natal ward. Each baby was accompanied with a 134 kHz RFID tag that was detected as the carrier passed through a portal and authorization and other details of the movement validated. However, the system was intermittent, failing to record ingress and egress movements properly, and even alarming when no baby was present. This was a huge security and logistical problem for the nursing staff. The LBA Interference Response Team determined that electrical devices in a switch room behind a wall adjacent to the portal were radiating interference as electrical devices were activated elsewhere in the hospital. The presence of this “hidden” electrical room has gone undetected by the vendor installation team. The solution was to prescribe an expensive electromagnetic shielding system.

· The case of the wacky stock picking robot – A West Coast manufacturer had a wild ride with its automated robotic inventory warehouse system. The robots traveled the aisles stocking product directly from a newly installed labeling/packaging line in the warehouse. These robots would pick product and deliver it to shipping location on request. After the new line was installed, robots often went on a binge, misreading RFID tags and mixing products on the shelves. It was driving both manufacturing and shipping crazy, and the RFID vendor was out of business and no help. An LBA Interference Response team was dispatched. We found that the new labeling line used high power ultraviolet light to instantly dry printed labels on product bottles. A high power 2500 MHz poorly shielded RF source was used to drive the ultraviolet lamps in the printer. The RFID tags and readers operated at 2500 MHz. Bingo! Unfortunately, the interference was too great to resolve with the existing layout, so the company relocated its ultraviolet labeling line to another building and forklifted product to feed the robots. Drastic, but problem solved.

· “Can you hear me now” – A North Carolina company made extensive use of several types of RFID systems in its warehousing operations. The logistics management got word that executive management was preparing to lease the warehouse roof space to a cellular operation and became concerned that the cellular frequencies might interfere with RFID operations. Based upon our study, LBA recommended using shielding paint on the roof under the proposed cell antennas to minimize ingress of cell frequencies to the RFID system. When the cell company balked at this protection, company management terminated rooftop rental discussions as the risks to the warehousing operations were financially far greater than any income from the antenna rental proposal. As a footnote, operators proposing RFID systems near communications sites and powerful radio broadcast stations should consider special RF interference precautions similar to those observed by cellular carriers to protect their equipment.

For more information on RFID system RF performance remediation and interference solutions available from LBA, contact Mike Britner at: 252-757-0279, mike.britner@lbagroup.com.


About LBA​:

LBA Group, Inc. has over 50 years of experience in providing RF asset solutions and risk management for industrial and telecommunications infrastructure assets. The company is comprised of LBA Technology, a leading manufacturer and integrator of radio frequency systems, lightning protection, and EMC equipment for broadcast, industrial, and government users worldwide; the professional technology consultancy Lawrence Behr Associates, and LBA University, providing on-site and online professional training. The companies are based in Greenville, N.C., USA.

Keep up with LBA on Facebook at: www.facebook.com/LBAGroup.


Contributing author: Christy Nelsen is a writer by profession with many articles published in diverse blogs and online publications. 

About The Author

Lawrence Behr is CEO of LBA Group and is an accomplished writer and public speaker on radio frequency matters. His experience with RF and electromagnetic compatibility matters spans over 50 years. He is an RCA Fellow and an SBE Fellow. Lawrence is a long-time amateur operation (K4JRZ) and enjoys hiking and canoeing.

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