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Comparing HF and UHF RFID technologies

The following white paper excerpts, authored by Texas Instruments, Inc. (www.ti-rfid.com), Philips Semiconductors (www.semiconductors.Philips.com/identification) and Tagsys (www.tagsyst.net), shed light on the myths and confusion surrounding RFID and addresses the choice of HF versus UHF technology for item-level pedigree pharmaceutical tracking. Part One of a two-part series.

More than pricing issues, more than insurance issues, drug counterfeiting is the one issue that attacks the very existence of pharmaceutical products. The speed of action by the Food & Drug Administration's taskforce on the issue and the aggressiveness of its recommendations point to packaging time and again. Read more at www.packagingdigest.com/info/ legal404

Executive summary

The numbers are astounding and the stakes couldn't be higher for consumers, pharmaceutical manufacturers, distributors and retailers. Up to seven percent of all drugs in the international supply chain may be counterfeit. Retail and pharmaceutical markets must absorb more than $2 billion in product returns each year, caused by overstocked or outdated products. Faced with some 1,300 recalls in 2001 alone, the industry is seeking ways to better monitor the international drug supply from "manufacturer to medicine cabinet."

The pharmaceutical industry is looking to radio frequency identification (RFID) as a primary way of solving these problems. RFID technology's ability to ensure the validity of data in the pharmaceutical industry is providing many new opportunities for reducing costs, while improving product quality and drug safety. The U.S. Food and Drug Administration's main interest in RFID is as a technology that can keep the drug supply safe and secure. According to the agency, RFID provides the most promising approach for reliably tracking, tracing and authenticating pharmaceutical products, and it is recommending widespread use of RFID in the pharmaceutical supply chain at the item level by 2007.

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Industry pilots involving several retailers, distributors and manufacturers have been launched, and some studies estimate that RFID-based solutions could save the industry more than $8 billion by 2006. In addition to anticounterfeiting, RFID benefits include improved inventory management through the reduction of out-of-stock items and safety stock, a decrease in shrinkage and diversion and faster, more efficient product recalls.

There has been much discussion about the potential of RFID in the pharmaceutical market. Up until now, much of the focus has been on passive tags in the ultra-high-frequency (UHF) band due to the Wal-Mart RFID mandate for case- and pallet-level supply-chain tracking, which requires the use of UHF technology. In support of this mandate, the industry is on track in 2004 to have its first global UHF RFID tag standard, known as EPC [Electronic Product Code] Gen 2 [Generation Two]. Manufacturers are developing tag and reader technology based on the new standard, and Wal-Mart suppliers are moving forward with RFID supply-chain pilots. In addition, EPCglobal, Inc. (www.epcglobalinc.org) is now turning its attention to the continuing development of existing EPC standards for high-frequency (HF), 13.56 mHz technology. There are a number of other established global standards developed by ISO/IEC for HF: item-level tracking, including ISO/IEC 180000-3; and ISO/IEC 15693.

Experts in the retail sector don't expect item-level RFID tagging of low-cost consumer goods to occur for five or more years. In the pharmaceutical market, there is a strong business case for item-level RFID tagging today, due to the higher value of products and margins relative to retail products, in addition to the inherent concerns surrounding product safety.

Despite RFID's high-profile backing, industry momentum and indisputable benefits, there are still many obstacles, misconceptions and issues to be resolved along the way. This includes the choice of which RFID technology to implement, and in particular, which frequency would be most appropriate. This paper sheds light on the myths and confusion surrounding RFID and addresses the choice of HF versus UHF technology for item-level pedigree pharmaceutical tracking. It also overviews some of the commercial pharmaceutical and healthcare field trials and implementations taking place.

Market drivers

The benefits of RFID go well beyond the fight against counterfeit drugs. The pharmaceutical industry relies on the integrity of many forms of data throughout the process of drug trials, manufacturing, distribution and retail sale. RFID's ability to uniquely identify each item (often called mass serialization) and securely capture data without line of sight throughout the supply chain has many benefits in the pharmaceutical industry including:

Insight, visibility and efficiency

At the item level, RFID can provide 100-percent visibility of inventory, no matter where it is in the supply chain, making it easier and quicker to move goods to the right place in the channel.

Accountability and brand protection

Having a more accountable supply chain at every point using RFID can dramatically reduce inventory losses and write-offs due to shrinkage. It is estimated that six to 10 percent of U.S. retail inventory is stolen or diverted. The technology can positively identify if returns were originally shipped from a particular manufacturer and at what price. RFID also helps prevent "gray market" distribution (products diverted to unauthorized channels), which costs companies and their customers hundreds of millions of dollars each year.

Product safety, recalls and regulatory requirements

In addition to anticounterfeiting, RFID can track both lot and expiration dates, improving expiration management. The technology can store pedigree information, satisfying regulatory requirements. By zeroing in on individual items and capturing manufacturing data, such as lot number and location information, RFID can significantly reduce time spent identifying products targeted for recall as well as reduce the likelihood of a mass market recall of branded products.

Advantages over bar codes

No matter the frequency used, RFID has several advantages over bar codes. Storage of reprogrammable data on a silicon chip that can be accessed through a wireless interface is a much more robust solution for automatic identification systems. With RFID, the radio signals are used to both power silicon chips as well as transmit data to and from them. Data can be read from passive, battery-less RFID chips in a range of distances from several inches up to 30 ft (9 m).

Advantages of RFID compared with bar codes include the following:

Simultaneous identification

Unlike other auto ID methods where items must be physcially separated or read individually, numerous RFID smart-label transponders can be read simultaneously—identifying multiple labels, containers or items all at the same time as they pass a reading location or are read using a hand-held scanner. This need is critical in supply-chain logistics, especially at the item-tagging level, where there could be 25 different items in a case traveling on a pallet with 30 other cases, passing through a tunnel reader or portal all at the same time. RFID is the only technology that can read individual items simultaneously.

Not line-of-sight

RFID provides a contactless data link without the need for line of sight. Thus, labels can be hidden or embedded in items, but still be read, which is impossible with auto ID methods, such as bar codes.

Data storage

RFID can store upwards of 30 times more data than bar codes, allowing the tag to carry a range of real-time information about an item at multiple points in the supply chain. Mass serialization, or the ability to store a unique serial number for each and every item, is something that cannot be accomplished with bar codes. Tag size is also a factor. To store all the data pharmaceutical companies would like to track at various points would require a large bar code—perhaps larger than the item it's adhered to— or may even require application of multiple bar codes.


RFID tags act as data carriers. Information can be written to and updated on the tag, which is specific to an item, container or pallet in the supply chain. This information is then held with that item, acting as a traveling item history or self-contained database. Read/write tags could also potentially provide a migration path to the EPC network once it has been built to support electronic track-and-trace using networked databases.

RFID solutions to counterfeit drugs could save more than $8 billion by 2006. At the item level, RFID can provide 100-percent visibility of inventory, which can reduce inventory losses and write-offs due to shrinkage.

Read reliability

First-pass accuracy is important in supply-chain applications. With RFID, the need for spending time scanning items multiple times is eliminated. Using other auto-ID technologies requiring line-of-sight, tags sometimes have to be run through the system a second time or be manually read.


Concerns about harsh or dirty environments may restrict other auto ID technologies.But the durability of RFID technology is suited to fit the needs of supply-chain and warehousing applications. In warehouses where harsh environments are common, RFID labels can be read through dirt, soil and other materials.

Difficult to replicate

While linear or 2D bar codes can be easily replicated by counterfeiters by simply scanning and printing them, the RFID tag-manufacturing process would require a great deal more expertise, investment and time to copy. Counterfeiters would potentially have to build or have access to a semiconductor wafer-fabrication facility in order to manufacture the chips and assemble them to inlays or labels. It would also require significantly more time to replicate the individual EPC serial numbers.

HF/UHF primer—physics and technology characteristics

Along with low-frequency (125 kHz to 134.2 kHz), passive RFID tags operate in the high-frequency band of 13.56 mHz and in the ultra-high frequency band of 860 to 960 mHz. Both types of tags derive the energy needed to operate from the antenna's radio-frequency signal.

This radio-frequency signal propagates from an antenna and comprises electromagnetic waves of energy. HF systems use the magnetic field to transfer power and data, while UHF systems use the electric field.

In HF systems, the magnetic filed powers up an RFID tag through a process known as induction. A magnetic field is created as a result of electrical current flow in a closed loop of electrically conductive material (e.g., copper tubing, copper tape, etc.) acting as an antenna. The magnetic field induces an electric current flowing on the antenna of an RFID tag that's within the magnetic field (also a closed, conductive loop). This induced electric current is then used to power the RFID tag's circuitry, enabling the interpretation of and response to commands sent to it from a reader.

Both types of tags derive the energy needed to operate from the antenna's radio-frequency signal. HF systems use the magnetic field to transfer power and data, whereas UHF systems use the electric field.

In UHF systems, the electric field powers up an RFID tag that enters an area within this field of energy. The power of the electric field is used for the RFID tag's circuitry in a fashion similar to what occurs with HF tags, but uses capacitive coupling.

Read range and read nulls

The intensity of the magnetic field in HF systems can be well defined for a specific read zone, but its relative strength falls off quickly as a function of distance from the antenna, equating to a short read distance of typically less than 5 ft in conventionally designed systems. In comparison, the electric field used in UHF systems has a relative strength that extends much farther, enabling read distances of up to 30 ft.

Fishnet versus Swiss cheese analogy

Due to areas known as field nulls, the UHF frequency's electric read zone isn't as well defined compared to that of a magnetic field. Detuning of the tags, which renders them ineffective, can occur when item-level tags are in close physical proximity to one another or have materials with high permittivity, such as liquids, or high reflectivity, such as metals (see next section). An analogy illustrates the difference between HF and UHF tags for item and pallet identification: picture the HF "signal" resonating as a fine fishnet wrapping around the tagged packages. Next, envision the UHF signal as a piece of Swiss cheese wrapping around the same tagged packages. The Swiss cheese, or field null phenomenon, requires the use of alternative techniques to compensate for these holes. The HF "fishnet" captures all of the tags, including those on items packed closer to the center of the package, while the UHF "Swiss cheese" interrogating signal misses many tags that may be positioned in the inner portion of a pack because they fall into these field nulls.

The feld nulls require use of a more complex signaling scheme, involving a common technique known as frequency hopping. Due to frequency hopping's longer read range, UHF technology may be more suitable for reading case and pallet tags from portal or conveyor antennas. HF technology's shorter read range allows for well-defined read zones that can facilitate small shelf and item-level applications.

Liquids and metals

High-frequency RF signals are more able to penetrate liquids because the longer wavelengths of HF systems are less susceptible to absorption. UHF's shorter wavelengths are more susceptible to absorption by liquids. In practical applications, HF tags are better suited for tagging water- or liquid-bearing containers. A UHF tag can be made to work, but its effective read range would be drastically reduced.

Metallic environments affect all RFID frequencies. Radio-frequency signals don't pass through metal, and when metallic materials are close to the reader's antenna or the tag's antenna, the characteristics of the system are changed. Metal changes the inductance of the antenna on HF and UHF tags and basically re-tunes its resonant frequency, reducing the overall read range. Another effect: RF energy is absorbed by the metal, instead of radiating through it.

While both frequencies cannot penetrate through metal, absorption affects HF tags and UHF tags differently.

Anti-collision and simultaneous reading of tags

Passive RF tags made to EPC Class-1 (write once, read many) and EPC Class-2 (multiple read/write) specifications, whether HF or UHF, will have a built-in anti-collision feature that enables multiple simultaneous reading of tags with greater than 90-percent accuracy at a rate of up to 1,000 tags/sec. These features are available on HF tags from several manufacturers. In pharmaceutical applications, anti-collision allows for all 100 individually tagged bottles in a package to be identified and read instantaneously without opening the package or using a hand-held reader to scan each item. The re-tuning phenomenon and the nature of RFID frequency physics, locating a tagged item within a small read —containing multiple tagged items—can be easier with HF due to field patterns and relative tag signals.

Memory and data storage

RF tags' storage capabilities come in many memory sizes and vary depending on the manufacturer. Several HF products offer anywhere from 96 bits up to 8K bytes of memory, enabling a "mobile database" application. Data is stored on the RFID tag instead of in a networked database. UHF products have data storage capabilities in the lower end of the range described, and are suitable for only carrying "license-plate" data.

Tag size and form factor

The size of bottles, vials, tubes and others dictates the need for a small, rigid, disc-module-type of RF tag, while blister-packs and multiple unit-dose packages may need larger, self-stick, flexible tags that can be laminated to paperboard, paper, plastic or other nonferrous materials. Where a foil seal is required, a small stand-off that creates an air gap may be used to insulate the tag from the disruptive properties of metal. Millions of HF tags have been proven to withstand liquid, pressure and precipitous temperature swings. But HF tags have shown satisfactory efficacy and are well suited for pharmaceutical applications due to their form-factor adaptability. Passive UHF tag implementations are still in their infancy, so it's unclear exactly what issues are yet to be explored.

Packaging and placement for anticounterfeiting protection

Adaptable, flexible and economical, EPC Class-1 and Class-2 tags are suited for assuring the drug's pedigree throughout the supply chain. Although the process would be most effective if covertly executed at the point of manufacture, two types of HF anticounterfeiting tags may be considered for introduction in the packaging and labeling of all drugs. Embedded, robustly designed and more diminutive tags of 9 mm dia or smaller can be injection-molded into plastic caps to address the need for concealment, eliminating the chance of tag removal by a would-be counterfeiter. These tiny tags could be passive, one-time-programmable (OTP) write-once, read many (ORM) or have a multiple-read/multiple-write memory. A benefit of an OTP device is low cost, but a database operating with the tag is required in order to track pedigree. With a multiple-read/write integrated circuit, all product-tracking information can be put on a tag and subsequently doesn't have to depend on the database and supporting background network for the information. The data stored is up to the user. It all boils down to the application's needs and the cost benefit realized from localized data written to the tag, stored at the database level or in both locations. Both scenarios could track, trace and assure authenticity from origin to end user.

In an upcoming issue: Environmental factors, global standards and requirements, privacy issues, tracking blood and other samples, hospital item management and more.

For Part 2 of this report, see RFID: HF versus UHF technologies, Part Two

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