Abstract: RFID (Radio Frequency Identification) technology has the potential to become a common and essential component in embedded system design. Beyond its traditional role in inventory management, recent advancements in RFID tags and high-speed, long-range readers allow embedded system designers to easily incorporate a variety of features, such as access control, anti-counterfeiting, convenient payment, medical authentication, dynamic pricing, product history, and remote asset tracking. Embedded RFID applications typically integrate readers into products or systems to add local data collection capabilities, enhancing the product's fundamental functionality. Today, embedded RFID applications are found in hotels, prisons, hospitals, retail outlets, farms, casinos, toll roads, factories, and various commercial and military vehicles. As embedded system developers recognize the value of this technology and adopt it in new designs, these non-traditional RFID applications will become commonplace.
With the help of a built-in RFID reader, the embedded system can exchange data with tagged items to create a new type of application that is in harmony with the environment.
Key Points
Although RFID dates back to the 1940s, the technology has not been able to realize its potential due to the lack of interoperability between proprietary products and the absence of relevant standards.
* Passive RFID transponders do not contain a power source; they rely on the incoming radio frequency signal to induce a small current in the antenna sufficient to transmit a response signal.
*Embedded RFID readers can interrogate transponders moving at high speeds and at distances exceeding 30m, depending on antenna size and transmission power.
Global standards and directives from government agencies and businesses have expanded the use of RFID; however, privacy and security concerns continue to hinder full adoption.
RFID (Radio Frequency Identification) technology has the potential to become a common and essential component in embedded system design. Beyond its traditional role in inventory management, recent advancements in RFID tags and high-speed, long-range readers allow embedded system designers to easily incorporate a variety of features, such as access control, anti-counterfeiting, convenient payment, medical authentication, dynamic pricing, product history, and remote asset tracking. Embedded RFID applications typically integrate readers into products or systems to add local data collection capabilities, enhancing the product's core functionality. Today, embedded RFID applications are found in hotels, prisons, hospitals, retail outlets, farms, casinos, toll roads, factories, and various commercial and military vehicles. As embedded system developers recognize the value of this technology and adopt it in new designs, these non-traditional RFID applications will become commonplace.
The concept of RFID emerged in the mid-20th century, and today it is poised to become the next major technology. As early as World War II, the U.S. military used early forms of RFID to distinguish friend from foe aircraft. The first commercial RFID applications appeared in the 1970s and 80s for tracking and identifying items within a single location. However, in these early RFID deployments, many developers based their applications on proprietary technologies, each using unique communication methods and requiring specialized reader hardware from companies that manufactured the tags. This lack of standardization led to industry fragmentation, slow adoption, and performance lagging behind the hype surrounding RFID technology. Today, developers are correcting most of these early problems, and RFID is becoming a growing industry with dedicated systems in logistics, access control, anti-counterfeiting, item-level inventory, contactless payments, and a variety of new embedded system applications.
One of the most basic and widespread uses of RFID technology is the EAS (Electronic Anti-theft System), which retailers use to wage a high-tech "war" against shoplifting. These crimes cost the industry billions of dollars annually, making it easy for retailers to justify purchasing expensive electronic systems to curb theft. EAS systems employ large antenna panels and security tags of various sizes; the former are installed at store exits, and the latter are attached to high-risk merchandise. The basic principle of all EAS systems involves the use of transmitters and receivers. The transmitter creates an electromagnetic field in the store exit area, while the receiver detects changes in that field. As a customer passes through the exit, a small tuning circuit or magnetic material within the security tag causes a sufficiently large change in the electromagnetic field that the receiver detects and triggers an alarm. After a customer purchases an item, the store clerk must remove the security tag or disable it to prevent the alarm from sounding when the customer leaves the store.
Reflection data
Most developers of newer RFID architectures use low-cost transponders (or tags) as the foundation of their architecture, consisting of an IC for data storage and communication, and an external antenna. Tags come in two basic types: passive and active. Passive tags contain no power source and rely on a small current induced in the antenna by the radio frequency signal from the reader, sufficient to transmit a response signal. RFID tags transmit data by altering the amount of reflected energy from the radio frequency signal from the reader. Passive tags can operate up to 30 feet, depending on the reader's power output, antenna configuration, and operating frequency. BielomaTIk's RF-LoopTag is an expandable antenna device that provides both short-range and mid-range passive RFID tags (Figure 1).
Active RFID tags with their own power source (such as an internal battery) can significantly extend the range. Active tags can transmit data at higher power levels and are generally more accurate than passive types. Active tags are typically used for high-value items such as military vehicles or containers. The antenna structure of an RFID system depends on the application, the environment during reading, and the operating frequency.
Government agencies have allocated several frequency bands for RFID, but these are not uniform globally. LF (Low Frequency) devices operate in the 125kHz to 134kHz range and are used in applications such as access control, animal identification, asset tracking, and vehicle security key cards. HF (High Frequency) 13.56MHz tags are used for applications with a reading distance of less than 3 feet. Unlike other bands, HF tags are less susceptible to interference when transmitting data near metal or water. The 860MHz–960MHz UHF (Ultra-High Frequency) band is popular in new applications because of its reading distance of 3m–5m and higher data exchange rates. Typical UHF applications include some asset tracking where tags are attached to pallets and containers, allowing operators to detect and record them as they pass through reader-equipped entrances.
Over the past few years, efforts have focused on creating a unified standard for tags and readers in each frequency band. ISO and IEC have created several RFID standards covering various aspects, including frequency, data encoding methods, and the use of RFID technology. For example, ISO/IEC 14443 and 15693 standards define communication interface protocols for RFID tags used in payment systems, contactless smart cards, and proximity cards. ISO has also created standards for performance testing of RFID tags and readers. Additionally, the ISO/IEC 18000 series includes dedicated air interface protocols for automatic identification systems and goods management systems used to track goods in the supply chain.
repeater
Several manufacturers produce RFID transponder chips used in tags. For example, Texas Instruments (TI) offers a line of Tag-itHF-1 transponder ICs that comply with the ISO/IEC 15693 global standard, which is geared towards product verification, access control, asset tagging, supply chain management, and ticketing applications. These products provide user-accessible memory and a comprehensive command set, the former with a capacity of up to 2048 bits, consisting of 64 blocks, and the latter used to select tags and read, write, or lock stored data. These devices identify multiple transponders appearing in the reader's radio frequency field through a factory-programmed and locked unique identifier. According to ISO/IEC 15693, ASK or FSK modulation operating at high or low data rates is used for communication between the reader and transponders, or for downlink communication. The transponder responds in the same way the reader queries it. This technology performs frame synchronization for both uplink and downlink communication and uses CRC checks to ensure their security.
Most embedded RFID applications require a dedicated reader as part of the design to interpret local tags. Vending machines are a good example of embedded RFID applications. These machines can accept contactless payments from RFID cards using a built-in reader. Additionally, if the items being sold are tagged, the machine can also know their inventory for automatic restocking. Small, low-cost embedded readers are crucial for these applications, and companies like TI, SkyeTek, and Parallax supply such readers. For example, Parallax, in collaboration with GrandIdeaStudio, has developed a low-cost RFID reader module that works in passive repeater tags for applications such as access control, automated identification, robotics, navigation, inventory tracking, payment systems, and car engine immobilizers (Figure 2). This module features a 2400bps serial port and requires a 5V DC power supply. Parallax readers start at under $40.
For more durable or industrial applications, GAORFID offers a UHF RFID reader that supports two external antennas (Figure 3). The 236002 model operates in the 902MHz–928MHz frequency band and is designed for high-speed warehousing, distribution, and manufacturing applications. This module can identify objects moving at 10m/s at a distance of 7m. The module requires 12V DC and communicates via a serial RS232 or Ethernet interface.
