RFID Frequently Asked Questions
AIM members from the RFID Experts Group answer the most asked questions we receive from those looking to learn more about RFID. Just click the question below to get more information, and if you would like even more details or have additional questions, contact us!
WHAT IS RFID?
Generally, there are three bands or categories commonly acknowledged within the industry. There’s an LF band, which is in the kilohertz range. There’s an HF band, which is in the low megahertz range. And then there are the UHF bands, which are in the upper megahertz range. In addition to that, there are two general categories referred to as active and passive. An active tag has a battery, while a passive tag does not. Regardless of whether we’re active or passive or what frequency range we’re working with, the reader will send out a signal, and any of the RFID tags (sometimes called transponders) will respond with a message back.
The big difference between active and passive is that passive systems do not have a battery, so they have to be queried by the reader. On the other hand, an active system is able to broadcast on its own but can also be queried by the system. The transponder will generally have a unique identifier to differentiate it from other transponders.
If I’m using an LF solution, you’ll often see those in the chips we put into our pets, like the microchips in the neck of your cat, dog, or horse. These LF tags work well around water, which is why they’re used. They use a magnetic solution known as an inductive solution for communication.
HF, which is the NFC solution you find out there, also has ISO standards associated with it. These systems are passive and respond with a modulated signal back to the RFID reader when queried. When the tag comes into range with the magnetic field generated by the reader, it will modulate that signal, and the reader can interpret it to identify the tag.
Generally, RFID systems tie the collected information to a back-end solution through software. This allows for data collection and lookup. Similar to having a license plate for your car, it’s crucial to have a supporting database for the system to be useful. Otherwise, it doesn’t provide much value.
The third type of passive system is the rain RFID mentioned earlier. It uses a reflective RF energy solution, similar to radar. The signal is sent out, bounced back by the tag, and modified for communication. It relies on a database to provide additional information. Even with the new standards introduced by EPC Global and GS1, there may be expiration dates or batch lots on the tag, but the item description itself is not stored in the tag. To identify the item, it looks up the information in the database.
So, even if I have a drink in front of me with a tag that reads “012000504082,” without a database to look it up, I don’t know what that drink is. It’s just a license plate reference.
HOW DOES AN RFID SYSTEM WORK?
An RFID system consists of a tag made up of a microchip with an antenna, and an interrogator or reader with an antenna. The reader sends out electromagnetic waves. The tag antenna is tuned to receive these waves. A passive RFID tag draws power from the field created by the reader and uses it to power the microchip’s circuits. The chip then modulates the waves that the tag sends back to the reader, which converts the new waves into digital data.
WHAT ARE SOME COMMON RFID APPLICATIONS?
The question of the most common applications for RFID often leads to an “it depends” type of answer. Unfortunately, you see it a lot in logistics, and where you’re seeing it a lot currently, as of this recording, is in things like apparel. The reason is that RF signals can easily pass through clothing. So, if you go to stores like Macy’s, Walmart, Target, or many apparel companies, and you start looking at the products on the shelves, they will have RFID tags. This is because, at the end of the day, it’s really hard for a person to differentiate between items like medium, large, or extra-large shirts, or socks that are size 8 to 10 versus 10 to 12, because they all look the same. RFID is a very effective way to manage inventory, significantly reducing the time store employees spend on determining what’s actually on the shelves. From an inventory point of view, this is a huge win and allows for increased productivity.
RFID can also be used in manufacturing to tag and identify items that may not easily accept a barcode due to factors like paint, dirt, or processes that don’t allow for barcodes to be used. We also see RFID tags heavily used in security for access control, and even in our passports. If you got a new passport in the last year or so, you’re likely to have an RFID tag, at least in the U.S.
We’re also seeing them on more and more luggage tags in airports. Certain carriers are incorporating RFID tags into the baggage tags for checked luggage. This enables easier tracking and ensures your bag gets to the right destination on time.
In warehouses, RFID tags are prevalent for tracking pallets and cases of product. Again, this allows team members to move, ship, receive, and count products without having to stop and scan barcodes with a handheld scanner. This boosts productivity and ultimately contributes to a more profitable operation.
Another significant use case for RFID is the concept of indoor GPS. Here at the new Auto ID lab at the University of Memphis, we have antennas in the ceiling that enable us to track the position of RFID tags as they move around the space. While it doesn’t provide millimeter-level precision, it’s excellent for locating larger items like a pallet of product or a piece of tooling. It allows me to narrow down the search area and find the item much more quickly.
WHAT IS THE DIFFERENCE BETWEEN LOW-, HIGH-, AND ULTRA-HIGH FREQUENCIES?
Just as your radio tunes in to different frequencies to hear different channels, RFID tags and readers have to be tuned to the same frequency to communicate. RFID systems use many different frequencies, but generally the most common are low-frequency (around 125 KHz), high-frequency (13.56 MHz) and ultra-high-frequency or UHF (860-960 MHz). Microwave (2.45 GHz) is also used in some applications. Radio waves behave differently at different frequencies, so it’s important to choose the right frequency for the right application.
HOW DO I KNOW WHICH FREQUENCY IS RIGHT FOR MY APPLICATION?
Different frequencies have different characteristics that make them more useful for different applications. For instance, low-frequency tags use less power and are better able to penetrate non-metallic substances. They are ideal for scanning objects with high-water content, such as fruit, but their read range is limited to less than a foot (0.33 meter). High-frequency tags work better on objects made of metal and can work around goods with high water content. They have a maximum read range of about three feet (1 meter). UHF frequencies typically offer better range and can transfer data faster than low- and high-frequencies. But they use more power and are less likely to pass through materials. And because they tend to be more “directed,” they require a clear path between the tag and reader. UHF tags might be better for scanning boxes of goods as they pass through a dock door into a warehouse. It is best to work with a knowledgeable consultant, integrator or vendor that can help you choose the right frequency for your application.
DO ALL COUNTRIES USE THE SAME FREQUENCIES?
No. Different countries have allotted different parts of the radio spectrum for RFID, so no single technology optimally satisfies all the requirements of existing and potential markets. The industry has worked diligently to standardize three main RF bands: low frequency (LF), 125 to 134 kHz; high frequency (HF), 13.56 MHz; and ultrahigh frequency (UHF), 860 to 960 MHz. Most countries have assigned the 125 or 134 kHz areas of the spectrum for low-frequency systems, and 13.56 MHz is used around the world for high-frequency systems (with a few exceptions), but UHF systems have only been around since the mid-1990s, and countries have not agreed on a single area of the UHF spectrum for RFID.
WHAT IS A CHIPLESS RFID TAG?
”Chipless RFID” is a generic term for systems that use RF energy to communicate data but don’t store a serial number in a silicon microchip in the transponder. Some chipless tags use plastic or conductive polymers instead of silicon-based microchips. Other chipless tags use materials that reflect back a portion of the radio waves beamed at them. A computer takes a snapshot of the waves beamed back and uses it like a fingerprint to identify the object with the tag. Companies are experimenting with embedding RF reflecting fibers in paper to prevent unauthorized photocopying of certain documents. Chipless tags that use embedded fibers have one drawback for supply chain uses—only one tag can be read at a time.
HOW MUCH DOES AN RFID TAG COST TODAY?
Most companies that sell RFID tags do not quote prices because pricing is based on volume, the amount of memory on the tag and the packaging of the tag (whether it’s encased in plastic or embedded in a label, for instance). Generally speaking, a 96-bit EPC inlay (chip and antenna mounted on a substrate) costs from 7 to 15 U.S. cents. If the tag is embedded in a thermal transfer label on which companies can print a barcode, the price rises to 15 cents and up. Low- and high-frequency tags tend to cost a little more.
WHAT INFORMATION CAN AN RFID TAG STORE?
It depends on the vendor and the application, but typically a tag carries no more than 2KB of data—enough to store some basic information about the item it is on. Companies are now looking at using a simple “license plate” tag that contains only a 96-bit serial number. The simple tags are cheaper to manufacture and are more useful for applications where the tag will be disposed of with the product packaging.
WHAT'S THE DIFFERENCE BETWEEN READ-ONLY AND READ-WRITE RFID TAGS?
Microchips in RFID tags can be read-write, read-only or “write once, read many” (WORM). With read-write chips, you can add information to the tag or write over existing information when the tag is within range of a reader. Read-write tags usually have a serial number that can’t be written over. Additional blocks of data can be used to store additional information about the items the tag is attached to (these can usually be locked to prevent overwriting of data). Read-only microchips have information stored on them during the manufacturing process. The information on such chips can never be changed. WORM tags can have a serial number written to them once, and that information cannot be overwritten later.
I HAVE HEARD THAT RFID DOES NOT WORK AROUND DIFFERENT MATERIALS, FOR EXAMPLE METAL AND WATER. DOES THAT MEAN I AM NOT ABLE TO USE IT TO TRACK CANS OR LIQUID PRODUCTS?
Radio waves bounce off metal and are absorbed by water at ultrahigh frequencies. That makes tracking metal products, or those with high water content, difficult. However, good system design and engineering are overcoming this. Low- and high-frequency tags work better on products with water and metal. In fact, there are applications in which low-frequency RFID tags are embedded in metal auto parts to track them.
WHAT IS EPC GEN 2?
Gen 2 is the shorthand name given to EPC Radio-Frequency Identity Protocols Generation-2 UHF RFID Standard. This standard describes the way passive UHF RFID tags (aka RAIN tags) communicate with the RFID readers. Primarily, it enables an RFID reader to select, inventory and access tags of interest. Many other commands can also help protecting data and consumer’s privacy as well as authenticating tags and readers for brand protection. Gen2 was designed to work internationally and has other enhancements such as a dense reader mode of operation, which prevents readers from interfering with one another when many are used in close proximity to one another. Gen2 has been endorsed as an ISO standard: ISO/IEC 18000-63.
HOW DOES EPC GEN 2 WORK?
The EPC (electronic product code) is a string of numbers and letters, consisting of a header and three sets of data partitions. The first partition identifies the manufacturer. The second identifies the product type (stock keeping unit or SKU) and the third is the serial number unique to the item. By separating the data into partitions, readers can search for items with a particular manufacturer’s code or product code. Readers can also be programmed to search for EPCs with the same manufacturer and product code, but which have unique numbers in a certain sequence. This makes it possible, for example, to quickly find products that might be nearing their expiration date or that need to be recalled.
WHY IS EPC TECHNOLOGY IMPORTANT?
EPC technology could dramatically improve efficiencies within the supply chain. The vision is to create near-perfect supply chain visibility—the ability to track every item anywhere in the supply chain securely and in real time. RFID can dramatically reduce human error. Instead of typing information into a database or scanning the wrong barcode, goods will communicate directly with inventory systems. Readers installed in factories, distribution centers, and storerooms and on store shelves will automatically record the movement of goods from the production line to the consumer.
HOW CAN A COMPANY TRACK ITEMS USING EPC GEN 2?
Companies have to create a network of RFID readers. In a warehouse for example, there could be readers around the doors on a loading dock and on every bay. When a pallet of goods arrives, the reader on the dock door picks up its unique license plate. Computers look up what the product is using the EPC Network. Inventory systems are alerted to its arrival. When the pallet is put in bay A, that reader sends a signal saying item 1-2345-67890 is in bay A.
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