Electronics & Scientific Guide, Technology Trends

UHF RFID Technology and its Applications

Radio technologies used in the Internet of Things can be extended to different business and living areas. UHF RFID applications, for example, enable the uncomplicated collection of toll data and accelerate car rental.

The effects of the Internet of Things (IoT) are often tangible on the consumer side with enhanced convenience and ease of use. Today, many people use contactless payment, a method that is possible through short-distance radio communication between a payment terminal and EC or credit cards, mobile phones or smartwatches also equipped with this technology.

The underlying wireless technology has the potential to change significantly more areas of our modern lives. One of the most established forms of radio communication used for IoT applications is RFID technology. Studies predict that the use of this technology in retailing by attaching RFID tags to garments will increase rapidly by the end of the century.

Products with RFID tags are recognized directly at the payment terminal. This makes purchasing easier for customers than before.

RFID technology has been on the market for several years. Their use in the area of IoT applications entails numerous synergy effects. Since each RFID device has a unique and unique identification number, it can be used to identify virtually any object. If the RFID reader is part of an integrated system, it offers almost unlimited potential for new applications. The market introduction of UHF RFID technology for the ultra-high frequency range has once again significantly increased this potential.

The UHF RFID technology at a glance

The contactless RFID technology works with a range of a few centimeters to several meters and uses the following frequency ranges: 120 to 150 kHz (low frequency or LF), 13.56 MHz (high frequency or HF) and 860 to 960 MHz (ultra high frequency or UHF). Previous applications such as identification, access control and payment systems are mostly based on passive RFID transponders. This means that the RFID transponder does not have its energy source, for example, a primary cell. This is the essential feature of the RFID transponder. In general, transponders operating in the LF and RF frequency ranges use the energy required by inductive coupling (near field), while UHF transponders use the electromagnetic wave propagation in the far field.

Standardization organizations such as ISO, IEC and EPC Global are working to establish standards to enable broader use of RFID technology. In 2009 ISO / IEC included the UHF EPC Gen 2 interface protocol defined by EPC Global for the UHF range in the ISO 18000-6 standard as a Type C operating mode. UHF RFID frequency bands vary across countries and range across frequencies between 860 and 960 MHz (EPC Global Standard).

The decisive characteristic for the performance of an RFID system is the range, i.,e. The maximum distance over which an RFID reader can either read information from the RFID tag or describe the day with data. The tag range of the RFID reader is defined as the read / write rate, expressed as a percentage of successfully read and write tags. The read/write rate varies with distance, but it also depends on the nature of the RFID reader and how signal propagation is affected by the environment of use.

In general, the ranges for reading and write operations are different because the transponder chip requires different amounts of energy for the two actions.

The biggest challenges in the development and deployment of a UHF RFID system, as explained below, are the execution of the reader and the passive tag.

Limiting factors of the tag:

  • The crucial limiting size of the tag is the sensitivity threshold of the chip. It is the minimum amount of received RF power needed to operate the RFID chip.
  • antenna gain
  • Antenna polarization: To achieve maximum range, the tag antenna and reader antenna must be matched about their polarization.
  • Matching the impedance between antenna and RFID chip

Limiting Factors of the Reader:

  • EIRP (equivalent isotropic radiant power): This determines the strength of the signal emitted by the reader in the direction of the day.
  • Reader Sensitivity: This is usually defined concerning a specific signal-to-noise ratio or error probability of the receiver.

In general, the range of passive UHF RFID systems is limited by factors such as tag features, signal routing environment, and RFID reader parameters. With high reader sensitivity usually outweighs the limiting factors of the day. However, the tag reach of the reader can be maximized by designing a high gain antenna that is well tuned to the chip impedance.

UHF RFID in IoT applications

In 2014, companies Google, Intel, Impinj, Smartrac, and AIM (the auto-identification industry) formed an international alliance to drive the adoption of UHF RFID systems as an IoT solution. The alliance today has over 160 members, including NXP Semiconductors. The alliance named Rain RFID uses the EPC Gen 2 standard by ISO / IEC 18000-63. A solution called Rain RFID uses UHF RFID technology that complies with that standard and is in line with Alliance goals.

Unicode DNA simplifies toll collection

The number of toll roads is steadily increasing worldwide. Tolls that allow expansion and maintenance of the road infrastructure help to avoid traffic congestion. Often road users have to stop at toll stations. Not so with the use of UHF RFID technology, which makes toll collection transparent.

In close cooperation, distributor Avnet Silica, system integrator Kathrein Solutions and Tönnjes vehicle identification specialist have successfully developed a system capable of driving individual vehicles on a highway with a range of 20 meters at speeds of up to 250 km / h capture. The system can be mounted on toll bridges over the motorway and collects data without any intervention in the traffic. This solution improves reliability and lowers the total cost of ownership (TCO) over an image-based approach using cameras and vehicle registration and recognition algorithms.

The newly developed system is a combination of the RRU 4500 UHF Rain RFID reader from Kathrein as well as the Ideplate label and Idestix label from Tönnjes. The technology complies with the Rain RFID standard and includes the NXP-developed UHF RFID system solution Unicode DNA. The side plate is a license plate that replaces the previous license plate and already contains the passive UHF RFID chip. The Idestix label is also a simple vignette equipped with this technology, which is glued to the inside of the windshield.

Rent faster cars with RFID

The use of RFID technology to locate objects can streamline processes. This also applies to the car rental. By equipping its rental cars with RFID technology, provider Sixt was able to reduce the time it takes to provide vehicle keys for car hire customers. Also, more accurate timestamps can be created for the return of rental cars, localized vehicles can be located more easily in the Sixt booking system, and car rentals can be made available to the respective customer more quickly.

The introduction of RFID technology has changed the way Sixt works with its 2200 rental stations and a fleet of over 144,000 rental cars. For example, customers who want to pick up their rental car at Sixt will now only have 20 seconds left on their keys instead of three minutes. Since many of the rental stations are located at airports, where more than 600 vehicles are rented per day, this time saving significantly improves the customer experience.

RFID and security

Any discussion about IoT must also address the need for security in an increasingly connected world. RFID technology is no exception. Already in the development phase, higher security levels about authentication and encryption were introduced. This also applies to the Avnet transponder Unicode DNA with UHF RFID technology from NXP.

The Unicode DNA significantly extends the security capabilities of the existing Unicode UHF RFID long-range portfolio and combines all functionality and security features in a single chip. The transponder includes two 128-bit AES keys that are securely stored on the chip and can be used by the on-chip AES accelerator for encrypted authentication. The keys are stored in a memory area that is locked during production. They can be generated by NXP or the customer and are typically used for tag authentication and tag group authentication.

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