What are the applications of passive RFID?

Passive RFID tags have been widely adopted, and some applications show creative adaptation to unmet needs.

While many uses for passive RFID tags were predicted and expected, innovators implemented some that were not obvious. This part will look at two of those applications.

Clothing-store “mass” checkout
One obvious application predicted for passive RFID labels was the replacement of the standard bar codes printed on routine items in the supermarket, but that hasn’t happened. The cost of printing the bar code on a label is zero, of course, and using a laser-based scanner works well enough; there is no clear advantage to RFID tags in that situation, except that the tags could be smarter and also have information such as “packed by” or “use by” date codes.

However, a leading fashion retailer had figured out what marketers call a “use case” for basic RFID labels. Uniqlo (their parent company is Japan-based Fast Retailing Co.), with 2400 worldwide stores, started using passive RFID tags to track individual clothing items and the entire received goods, warehousing, and ship-to-store cycle in the early 2000s. Beginning in 2017, Uniqlo had a tag sewn or attached to every individual garment, with RFID readers installed at warehouses, distribution centers, and stores, enabling real-time insight into product location, destination, availability, and even qualities like color and size. The UHF-band tags cost between 2 and 4 cents each.

Different tag styles and sizes are used for different sizes/weights of clothing items, but they are all RFID identical (Figure 1).

Figure 1. The RFID tags used by Uniqlo have different sizes and form factors to match the requirements of the different clothing items being scanned (Image: SEIKO RFID Technology Ltd.).

It’s one thing to use RFID in the invisible “back side” inventory management and shelf-stocking process, but Uniqlo took it one step further: customer self-checkout. Instead of customers or a clerk scanning a bar code on each item, the customer literally dumps all her purchases into a bin at the checkout desk and closes the lid (Figure 2). Within a few seconds, all the tags are then scanned as one batch, and the total bill is presented on the screen so the customer can review, approve, and pay.

Figure 2. The RFID self-serve checkout at Uniqlo is the reader bin integrated with the checkout screen (Image: Impinj).

The Uniqlo installation uses tags and a system provided by Impinj, Inc., using the RAIN RFID standard. RAIN RFID is a global alliance promoting the universal adoption of UHF RFID technology in a way similar to other wireless technology organizations including NFC Forum, WiFi Alliance, and Bluetooth SIG. RAIN uses the GS1 UHF Gen2 protocol which ISO/IEC has standardized as 18000-63. The word RAIN — an acronym derived from RAdio frequency IdentificatioN — is intended as a nod to the link between UHF RFID and the cloud.

What do the numbers show about the benefits and acceptance of this dump” self-checkout? Uniqlo says it has been only positive. First, checkout lines have been reduced during busy periods by 30 to 50 percent. Customers apparently like it as well: typically, over half of the customers use this self-checkout, and in some stores, that number typically reaches 80 to 90%.

What about golf?
Golf is obviously a popular sport, and practice hitting bays where players can enhance their long-range driving are important tools for players to keep in shape and improve their long game. Venues such as Top Golf provide this opportunity; and their newest one, opened in late 2023, features a three-story, year-round, 8 am to 11 pm practice facility with 90 hitting bays (three rows of ten bays), each equipped with heaters, fans, and the company’s Toptracer technology (Figure 3). Like the Uniqlo system, it uses RAIN RFID devices from Impinj — but in a very different way.

Figure 3. The tees at Top Golf are large, well-lit, heated, have a refreshment stand, and are equipped with a large-screen display showing statistics and analysis keys to the individual player (Image: Top Golf).

Using facility-provide clubs or your own set, you hit the balls which then score themselves, using a system based on passive RFID technology. Each ball has an embedded RFID tag which is used to track the ball’s landing (Figure 4).

Figure 4. The Top Golf system begins with a tiny RFID tag carefully packed into a golf ball which has also been modified to slightly degrade its flight performance (Image: Reddit).

Instead of physical signs to mark the yardage, there are several hundred RFID readers in the field, forming the various landing zones. The object is not to simply hit the ball as far as possible but to have each land at a desired target zone. Each zone is a circular net with sections, and the closer the hit ball gets to the center of the zone, and the further the zone is in the field (up to 240 yards), the more points you earn. When a ball falls into a zone, the readers scan its RFID chip, and the data is passed back to the Topgolf system to register.

After the raw data has been captured, the many scoring and analytic functions take over to characterize the results in various ways and present them to the golfer. This system keeps track of the scores of approximately 550 people when a complex is at capacity, each with 20 shots to record. The RAIN RFID system can manage over 10,000 ball reads per hour.

The balls themselves are based on standard Calloway balls. In addition to the embedded RFID microchip, which adds a fraction of a gram to the ball, the balls are “flighted” (detuned), so they travel 25 to 50 yards less than ordinary golf balls used on a course. The RFID technology can track the location of each ball, making it easy for staff to locate misplaced balls or see ones that have been “accidentally” packed and so might leave the premises.

The RFID readers in the Impinj Speedway series monitor each of these sub-targets. There are approximately 600 to 700 “read points” throughout the entire complex, keeping track of where the ball hits and automatically giving players the correct score.

While passive RFID was originally looked upon as fairly limited in scope, perhaps offering a way to replace bar codes, do end-to-end asset tracking, and replace card swiping, it has become much more. The two examples show how it has replaced the one-by-one checkout-scanning process and also enabled a new type of golf practice arrangement with detailed visuals and statistics.