The hottest RFID technology has the potential to b

RFID technology has the potential to become an important part of embedded system design. How should you act on RFID technology in embedded design

the idea of RFID appeared in the mid-20th century, and now it is about to become the next major technology. As early as the Second World War, the U.S. military used RFID in its early form to distinguish between enemy and our aircraft. The first commercial RFID applications emerged in the 1970s and 1980s to track and identify items in a single location. However, in the early deployment of RFID, many RFID application developers take proprietary technology as their basis, each of which uses a unique communication method, and requires the company that produces the tag to provide special reader hardware. The lack of standardization leads to the decentralization of the industry, slow adoption, and the actual performance lags behind the hype of RFID technology. Today, developers are correcting most of the early problems. RFID has also become a growing industry, with special systems in logistics, access control, anti-counterfeiting, item level inventory, contactless payment and a variety of new embedded system applications

reflected data

most developers of newer RFID architectures use low-cost transponders (or tags) as the basis of the architecture. They consist of an IC for data storage and communication and an external antenna. There are two basic types of labels: passive and active. The passive tag does not contain power supply, and relies on the RF signal from the reader to induce a small current in the antenna, which is sufficient to transmit a response signal. RFID tags transmit data by changing the reflected energy of the RF signal from the reader. The working distance of the passive tag can reach 30 feet, which depends on the power output of the reader, antenna structure and working frequency. Bielomatik's RF looptag is an expandable antenna device that provides both short-range and medium-range passive RFID tags (Figure 1)

figure 1

active RFID tags with their own power supply (such as internal batteries) can be used to significantly extend the distance. Active tags can transmit data at a higher power level and are generally more accurate than passive types. Active tags are generally used for high priced items such as military vehicles or containers. The antenna structure of RFID system depends on the application, the environment during reading and the working frequency

government departments have allocated several frequency bands for RFID, but they are not unified in the world. LF (low frequency) devices work in the range of 125kHz to 134khz, and are used in access control, animal identification, asset tracking, car security key card and other applications. H Electromechanical is the soul of all components. F (high frequency) 13.56MHz label is used for applications with reading distance less than 3 feet. Unlike other frequency bands, HF tags are not susceptible to interference when transmitting data near metal or water. 860MHz ~ 960MHz UHF (ultra high frequency) band is very popular in new applications because its reading distance is 3M ~ 5M and its data exchange rate is higher. Typical UHF applications include some asset tracking, in which tags are hung on pallets and containers. When they pass through the entrance equipped with readers, operators who can perform performance and strength tests on Leeper's existing prostheses can find them and make records

over the past few years, people have focused on creating a unified set of standards for tags and readers in each band. ISO and IEC have created several RFID standards including frequency, data coding method, RFID technology use and so on. For example, iso/iec14443 and 15693 standards define communication interface protocols for RFID tags used in payment systems, contactless smart cards, and proximity cards. ISO also created standards for performance testing of RFID tags and readers. In addition, the iso/iec18000 series includes a dedicated air interface protocol between the automatic identification system for tracking supply chain goods and the item management system

transponder

several manufacturers produce RFID forwarding chips used in labels. For example, Texas Instruments Corporation (TI) provides a tag-ithf-1 Transponder IC product line, which conforms to the iso/iec15693 global standard, which is oriented to product verification, access control, asset labeling, supply chain management, and ticketing applications. These products provide user accessible memory and a wide range of command sets. The former has a capacity of 2048bit and consists of 64 blocks. The latter is used to select labels and read, write or lock stored data. These devices identify multiple transponders that appear in the RF field of the reader through a factory programmed and locked unique identification code. According to iso/iec15693, ask or FSK modulation working at high data rate or low data rate is used to complete the communication or downlink communication between the reader and the transponder. The transponder answers in the same way that readers ask it. This technology performs frame synchronization for uplink communication and downlink communication, and uses CRC check to ensure their safety

most embedded RFID applications require a dedicated reader as part of the design to interpret local tags. Vending machine well illustrates the application of embedded RFID. This machine can accept contactless payment of RFID card with the help of built-in reader. In addition, if the items on sale are labeled, the machine can also know their inventory, so as to automatically order replenishment. Small low-cost embedded readers are critical for these applications, and Ti, skyetek, parallelax and other companies supply such readers. For example, a low-cost RFID reader module developed by parallelax in cooperation with grandideastudio works in passive transponder tags for access control, automatic identification, robots, navigation, inventory tracking, payment systems, car engine anti-theft locks and other applications (Figure 2). The module has 2400bps serial port and requires 5V DC power supply. The parallax reader starts at less than $40

figure 2

for more durable applications or industrial applications, gaorfid provides a UHF RFID reader that supports two external antennas (Figure 3). The 236002 type works in the 902mhz ~ 928mhz frequency band and is oriented to high-speed storage, distribution and manufacturing applications. The module can recognize objects moving at a speed of 10m/s at a distance of 7m. The module requires 12V DC voltage and communicates through serial RS232 or Ethernet interface

figure 3

embedded RFID technology is also very suitable for fast desktop gambling, in which cheating and manipulation are difficult to detect. With the help of appropriate data recording tools, casino operators can monitor the actions of gamblers in order to detect the count of playing cards, adjust rewards, and minimize the mistakes of the dealer. For example, internationalgametechnology and progressivegaming international jointly developed tableid desktop gambling automation system, which combines a software based desktop manager and a series of RFID chip scanning modules. The latest RFID gambling chip works at 13.56MHz, with a storage capacity of more than 10kbit. During gambling, the chip reader at each location recognizes and records the bets of each gambler. Tableid system calculates the betting mode of gamblers, summarizes the activities of licensees, and records the decisions made by gamblers every hour. The system can automatically update the average bet and win/loss records without user intervention. Several suppliers are manufacturing RFID based gambling coins suitable for table automation. For example, get the material properties: all indoor temperatures of the model experiment are basically maintained at 2025egamingpartnersinternational company is producing safechipbybourgogneetgrasset (Fig. 4)

Figure 4

RFID technology is beginning to replace traditional bar codes in many applications. For example, some libraries have begun to use RFID tags instead of bar codes to identify book titles, abstracts, database information and other information. During the transition period, the combined system can read bar codes or RFID tags when readers leave the library. Compared with barcode, RFID system provides several advantages, such as eliminating the line of sight requirements, allowing multiple tags to be read at the same time, and larger data storage capacity. RFID tags can also act as security devices to ensure that all borrowed books have been properly recorded before leaving the library. RFID tags can be applied to library cards to enable readers to handle the check-out procedures by themselves, thereby further simplifying borrowing

chipless RFID

manufacturers have demonstrated several RFID systems without Transponder IC. For example, manufacturers can embed aluminum fibers under printed documents or packages in a specific way to introduce the most easily damaged parts: packaging materials, so that these fibers can reflect RF signals with identification data. Another chip free system requires the use of tiny chemical particles with different magnetism. These chemical particles become active when exposed to the electromagnetic wave of the reader and emit a unique signal, which the reader interprets as a binary number. With up to 70 available chemicals, the reader can interpret its unique binary number based on the chemical mixture embedded in the item. Printed electronic technology can also deposit the forwarding circuit and antenna directly from the special inkjet or high-speed printer onto the production items or their packaging, so as to create labels that cooperate with RFID and barcode readers

when RFID applications extend to the consumption level, designers must consider privacy issues. For example, readers located in key locations can secretly ask for a variety of smart cards, key cards, passports and transponder tags using RFID technology. Similarly, when common items such as clothing and accessories become traceable, marketing experts can easily install low-cost readers in stores