RFID Knowledge

- May 28, 2018-

Radio Frequency Identification (RFID) technology, also known as radio frequency identification (RFID), is a communication technology that can identify specific targets and read and write related data through radio signals without identifying the mechanical or optical contact between the system and a specific target. . Commonly used low-frequency (125k ~ 134.2K), high-frequency (13.56Mhz), UHF, microwave and other technologies. RFID readers are also divided into mobile and stationary. Currently, RFID technology is widely used, such as libraries, access control systems, and food safety traceability.

1 Introduction

(English: Radio Frequency IDentification, abbreviation: RFID) is a kind of wireless communication technology that can identify specific targets and read and write related data through radio signals without identifying the mechanical or optical contact between the system and a specific target.

The radio signal is transmitted through a radio frequency electromagnetic field and transmitted from a label attached to the item to automatically identify and track the item. Some tags receive energy from the electromagnetic field emitted by the recognizer when they are identified, and do not require a battery. Also, the tag itself has a power source and can actively emit radio waves (electromagnetic fields tuned to a radio frequency). The tag contains electronically stored information that can be identified within a few meters. Unlike the barcode, the radio frequency tag does not need to be within the line of sight of the identifier, but it can also be embedded within the object being tracked.

Many industries use radio frequency identification technology. Attaching the tag to a car in production, the factory can easily track the progress of the car on the production line. The warehouse can track where drugs are located. RFID tags can also be attached to livestock and pets to facilitate positive identification of livestock and pets (active recognition means preventing the same identity from being used by several animals). RFID identification cards allow employees to access locked building parts, and RF transponders on cars can also be used to collect toll roads and parking fees.

Some radio frequency tags are attached to clothing, personal belongings, and even implanted in the body. Because this technology may read personal information without my permission, this technology also has the infringement of personal privacy concerns.

Conceptually speaking, RFID is similar to bar code scanning. For bar code technology, it attaches an encoded bar code to an object and uses a dedicated scanning reader to transmit information from bar magnetic to scan reading using optical signals. Writers; while RFID uses dedicated RFID readers and specialized RFID tags that can be attached to objects, using frequency signals to send information from RFID tags to RFID readers.

2, the structure

Structurally speaking, RFID is a simple wireless system with only two basic components. The system is used to control, detect and track objects. The system consists of an interrogator and many transponders.

Initially in the technical field, transponders are electronic modules that can transmit information to reply information. In recent years, due to the rapid development of radio frequency technology, transponders have new ideas and meanings, and are also called smart labels or tags. The reader of the RFID electronic tag communicates wirelessly through the antenna and the RFID electronic tag, and can read or write the tag identification code and memory data. RFID technology can identify high-speed moving objects and can identify multiple labels at the same time. The operation is quick and easy.

In the future, the China Internet of Things school-enterprise alliance believes that the rapid development of RFID technology is of great significance to the progress in the field of Internet of Things.

3, part of the transponder: the antenna, the coupling element and the chip, in general, are used as a transponder tag, each tag has a unique electronic code, attached to the object to identify the target object.

Reader: A device consisting of an antenna, a coupling element, and a chip that reads (sometimes writes) tag information. It can be designed as a handheld rfid reader (eg C5000W) or a stationary reader.

Application software system: It is an application layer software. It mainly deals with the collected data and is used by people.

4, characteristics of radio frequency technology features

The most important advantage of radio frequency identification systems is non-contact recognition, which can read through the harsh environment where snow, fog, ice, paint, dust, and bar codes cannot be used, and the reading speed is extremely fast, in most cases less than 100 milliseconds. The ability to write active RFID systems is also an important advantage. Can be used for process tracking and maintenance tracking and other interactive services.

The main issue that hampers the development of RFID systems is incompatible standards. The main manufacturers of radio frequency identification systems provide dedicated systems, resulting in different applications and different industries adopting different vendors' frequency and protocol standards. This confusion and segregation have already constrained the growth of the entire RFID industry. Many European and American organizations are working to solve this problem and have achieved some success. Standardization will certainly stimulate the significant development and widespread application of radio frequency identification technology.

Applicability in logistics management

The essence of logistics management is to achieve the two goals of reducing costs and improving service levels through the management of the entire logistics process. How to ensure that the right customers get the right products at the right time and in the right place with the right cost and the right conditions has become the highest goal pursued by logistics companies. In general, the value of an enterprise's inventory accounts for about 25% of the total assets of the company and accounts for more than 50% of the company's current assets. Therefore, the core of logistics management is the management of inventory in the supply chain.

The use of radio frequency identification technology in transport management requires only the installation of electronic tags on the outer packaging of goods, and the installation of readers at transport checkpoints or transit stations to enable the visual management of assets. At the same time, the owner can access the on-site visualization web page according to his authority to understand the specific location of the goods, which is of great significance to improving the service level of logistics companies.

Performance characteristics

1. Quick scan. The RFID identifier can recognize and read several RFID tags at the same time.

2. The size is small and the shape is diversified. RFID is not limited by size and shape in reading, and does not need to match the fixed size and print quality of the paper for reading accuracy. In addition, RFID tags can be developed in smaller and more diverse forms to be applied to different products.

3. Pollution resistance and durability. The carrier of traditional bar code is paper, so it is easily contaminated, but RFID is very resistant to substances such as water, oil and chemicals. In addition, because barcodes are attached to plastic bags or over-wrapped cartons, they are particularly vulnerable to breakage; RFID tags store data in the chip and are therefore protected from contamination.

4. Can be reused. Now that barcodes cannot be changed after printing, RFID tags can repeatedly add, modify, and delete data stored in RFID tags to facilitate information updates.

5. Penetrating and non-barrier reading. When covered, RFID can penetrate non-metallic or non-transparent materials such as paper, wood, and plastic, and is capable of penetrating communication. Barcode scanners must read barcodes at close range and without object obstruction.

6. The data memory capacity is large. The capacity of one-dimensional bar code is 50 Bytes, the maximum capacity of 2D bar codes can store 2 to 3,000 characters, and the largest capacity of RFID is MegaBytes. With the development of memory carriers, the data capacity has also been continuously expanding. The amount of data required to carry future items will increase, and the demand for the capacity of the labels to expand will increase accordingly.

7. Security. Since RFID carries electronic information, its data content can be protected by passwords, making its content less susceptible to counterfeiting and alteration.

RFID has attracted attention due to its features such as remote reading and high storage capacity. It can not only help a company significantly improve the efficiency of goods and information management, but also allow sales companies and manufacturing companies to interconnect, so as to receive feedback information more accurately, control demand information, and optimize the entire supply chain [3].

working principle

The basic working principle of RFID technology is not complicated: after the tag enters the magnetic field, it receives the RF signal from the reader, and sends the product information stored in the chip (passive tag, passive tag or passive tag) according to the energy obtained by the induced current. Or, the tag actively transmits a certain frequency signal (active tag, active tag or active tag). The reader reads the information and decodes it, and sends it to the central information system for data processing.

A complete RFID system consists of three parts: a reader and a tag (TAG), a so-called transponder, and an application software system. The working principle is that Reader emits a specific frequency. The radio wave energy is given to the Transponder to drive the Transponder circuit to send the internal data. At this point, the Reader receives the decoded data in sequence and sends it to the application program for processing.

The communication between the RFID card reader and the electronic tag and the energy sensing method can be roughly divided into two types: Inductive Coupling and Backscatter Coupling. Most low-frequency RFIDs use the first type, and higher frequencies use the second method.

The reader can be a read or read/write device depending on the structure and technology used, and is an RFID system information control and processing center. The reader is usually composed of a coupling module, a transceiver module, a control module, and an interface unit. Half-duplex communication is generally used for information exchange between the reader and the transponder, and the reader is coupled to the passive transponder to provide energy and timing. In practical applications, management functions such as collection, processing, and remote transmission of object identification information may be further implemented through Ethernet or WLAN. The transponder is the information carrier of the RFID system, and the transponder is mostly composed of coupling originals (coils, microstrip antennas, etc.) and microchips constituting a passive unit. [4] 6 Product Categories There are about three major categories of products derived from RFID technology: passive RFID products, active RFID products, and semi-active RFID products.

The development of passive RFID products is the earliest, and it is also the product with the most mature development and the most widely used market. For example, bus cards, cafeteria meal cards, bank cards, hotel access cards, second-generation ID cards, etc., which can be seen everywhere in our daily lives, are close-contact type recognition. The main operating frequency of its products are low frequency 125KHZ, high frequency 13.56MHZ, UHF 433MHZ, UHF 915MHZ.

Active RFID products have been gradually developed in recent years. Their long-distance automatic identification characteristics determine their enormous application space and market potential. In the field of long-distance automatic identification, such as smart prisons, smart hospitals, smart parking, intelligent transportation, smart cities, smart world and the Internet of things, there are major applications. Active RFID has emerged in this field and belongs to the category of long-distance automatic identification. The main operating frequency of the product is UHF 433MHZ, microwave 2.45GHZ and 5.8GHZ.

The different characteristics of active RFID products and passive RFID products determine different application fields and different application modes, and also have their own advantages. However, in this system, we focus on introducing semi-active RFID products between active RFID and passive RFID. This product integrates the advantages of active RFID and passive RFID in the management of access control and accurate positioning of personnel. , Regional positioning management, perimeter management, electronic fences and security alarms and other fields have great advantages.

Semi-active RFID products, combined with the advantages of active RFID products and passive RFID products, enable microwave 2.45G to take advantage of the low-frequency 125KHZ frequency trigger. Semi-active RFID technology, also known as low-frequency activation trigger technology, uses low-frequency, near-distance precise positioning, microwave remote identification, and uploading data to solve the problems that simple active RFID and passive RFID have no way to achieve. To put it simply, it is to activate positioning, identify and upload data at a short distance [5].

7. Advantage RFID is a flexible application technology that is easy to operate, simple and practical, and is particularly suitable for automation control. Freedom to work in all kinds of harsh environments: Short-range RF products are not afraid of bad environment such as oil stains and dust pollution. They can replace bar codes, such as tracking objects on the factory's assembly line; long-range RF products are mostly used for traffic, and the distance can be identified. Up to tens of meters, such as automatic charging or identification of vehicle identities. The radio frequency identification system mainly has the following system advantages:

Reading is quick and easy: The reading of the data does not require a light source, and can even be performed through the outer packaging. The effective identification distance is larger. When the active label with its own battery is used, the effective identification distance can reach more than 30 meters;

Fast recognition speed: When the tag enters the magnetic field, the reader can instantly read the information, and can process multiple tags at the same time to realize batch identification;

Large data capacity: The two-dimensional barcode (PDF417) with the largest data capacity can only store up to 2725 digits; if it contains letters, the amount of storage will be less; RFID tags can be expanded to dozens of K according to the needs of users;

Long service life and wide range of applications: Its radio communication means can be used in dusty, oily and other highly polluted and radioactive environments, and its closed packaging greatly extends the life span of printed barcodes;

Tag data can be changed dynamically: The programmer can write data to the reader, giving the RFID tag the power of an interactive portable data file, and it can write less time than a printed bar code.

Better security: not only can be embedded or attached to different shapes and types of products, but also can set password protection for reading and writing of tag data, thus having higher security;

Dynamic real-time communication: The tag communicates with the reader at a frequency of 50 to 100 times per second. Therefore, as long as the RFID tag is attached to an object within the effective recognition range of the reader, it can dynamically track and monitor its position. [6].

8, interface protocol air interface

Air interface communication protocol specification The information exchange between the reader and the electronic tag is aimed at producing interconnection and interoperability between devices from different manufacturers. ISO/IEC develops five kinds of frequency band air interface protocols, this idea fully reflects the relativity of the standard, a standard is a common demand for a wide range of application systems, but not all application system requirements, a set of standards can meet more A wide range of application needs.

ISO/IEC 18000-1 Information technology - Radio frequency identification based on single product management - Reference structure and standardized parameter definitions. It regulates the communication parameters of readers and tags that are commonly observed in the air interface communication protocol, and the basic rules of intellectual property. In this way, the standard corresponding to each frequency band does not need to repeat the same content.

ISO/IEC 18000-2 Information Technology - Radio Frequency Identification Based on Single Item Management - Suitable for Intermediate Frequency 125 to 134 KHz, Specified Between Tag and Reader