The reader/writer, also known as the RFID tag reader/writer, is one of the two important components of an RFID system. RFID reader devices are commonly referred to by other common names based on their specific functions, such as readers, interrogators, communicators, scanners, readers, programmers, readers, portable readers, AEI devices, etc. Generally speaking, the reading and writing devices for RF tags should be designed according to the reading and writing requirements and application needs of the RF tags. With the development of radio frequency identification technology, some typical system implementation modes of radio frequency tag readers have been formed. The focus of this chapter is to introduce the implementation principle of this reader/writer. From the most basic principle, RFID tag reading and writing devices generally follow the basic pattern shown in the figure.
There are two main working modes of a reader/writer: one is that the reader/writer speaks first, and the other is that the tag speaks first.
Under normal circumstances, electronic tags are in a waiting or sleep state. When the electronic tag enters the range of the reader and is activated, it changes from a sleep state to a receiving state, accepts commands sent by the reader, performs corresponding processing, and returns the results to the reader. This type of electronic tag that only sends data after receiving special commands from the reader/writer is called RTF mode; On the contrary, entering the energy field of the reader, that is, the electronic tag actively sending data, is called TTF mode.

RFID is a flexible application technology that is easy to control, simple and practical, especially suitable for automation control. Can work freely in various harsh environments: Short distance RF products are not afraid of oil and dust pollution and can replace barcodes, such as tracking objects on factory assembly lines; Long distance RF products are commonly used in transportation, with recognition distances of up to tens of meters, such as automatic toll collection or vehicle identification. RFID systems have the following advantages:

  Convenient and fast reading: Data can be read without the need for a light source, and can even be read through the outer packaging. The effective recognition distance is larger, and when using active tags with built-in batteries, the effective recognition distance can reach more than 30 meters;
Fast recognition speed: As soon as the tag enters the magnetic field, the reader can instantly read the information and process multiple tags simultaneously, achieving batch recognition;
Large data capacity: The largest 2D barcode (PDF417) can only store up to 2725 numbers; If letters are included, the storage capacity will be less; RFID tags can be extended to 10K according to user needs;
Long service life and wide application range: Its wireless communication method enables it to be used in highly polluted and radioactive environments such as dust and oil pollution. Its enclosed packaging makes its service life much longer than printing barcodes;
Tag data can be dynamically changed: Programmers can write data to tags, giving RFID tags the function of interactive portable data files, with less writing time than printing barcodes;
Better security: not only can it be embedded or attached to products of different shapes and types, but it can also be password protected for reading and writing label data, providing higher security;

The most important advantage of RFID systems is non-contact identification. It can read labels in harsh environments where snow, fog, ice, paint, dirt, and barcodes cannot be used, with extremely fast reading speeds of less than 100 milliseconds in most cases. The fast write capability of active RFID systems is also an important advantage. It can be used for interactive services such as process tracking and maintenance tracking.  
RFID has attracted much attention due to its long-distance reading and high storage capacity. It can not only help a company greatly improve the efficiency of goods and information management, but also connect sales and manufacturing enterprises, thereby more accurately receiving feedback information, controlling demand information, and optimizing the entire supply chain.  
According to the structure and technology used, the reader can be a reading or reading/writing device, which is the information control and processing center of the RFID system. Readers typically include coupling modules, transceiver modules, control modules, and interface units. Generally, half duplex communication is used, where information is exchanged between the reader and the responder. The reader provides energy and timing to the passive responder through coupling. In practical applications, the collection, processing, and remote transmission of object recognition information can also be managed through Ethernet or wireless LAN. The responder is the information carrier of the RFID system. Most repeaters are passive units composed of coupling elements (coils, microstrip antennas, etc.).

In order to enable RFID to play an important role in the entire logistics supply chain, the ISO TC122 Packaging Technology Committee and the ISO TC104 Freight Container Technology Committee have established a JWG joint working group to develop a series of logistics supply chain standards. According to the application requirements, the working group has developed six application standards for the freight container, loading unit, transportation unit, product packaging, and five level logistics unit of a single product.

1) 1) Application requirements of ISO 17358
This is the application requirement standard for RFID in the supply chain, chaired by the TC122 Technical Committee and currently under development. This standard defines the parameters of each level of the supply chain logistics unit and defines environmental identification and data flow.

2) ISO 17363~17367 series standards
The series of standards for RFID logistics units in the supply chain respectively specify the RFID applications for freight containers, recyclable transport units, transport units, product packaging, and product labels. The content of this series of standards is basically similar. For example, the air interface protocol adopts the ISO/IEC 18000 series standards. There are differences in specific regulations, and supplementary regulations should be made for different users, such as environmental conditions, label size, label posting location, and other characteristics. Depending on the object, the carrier frequency of the electronic tag is required to be different. Freight containers, recyclable transport units, and electronic labels used by transport units must be reused. Product packaging is determined based on actual conditions, and product labels are usually disposable. In addition, data integrity, visual recognition, etc. It should also be considered. Recyclable units require higher data capacity, security, communication distance, and other aspects. This series of standards is currently being developed.
What needs to be noted here is the relationship between ISO10374, ISO18185, and ISO17363. They are all for containers, but ISO10374 is for container management, ISO18185 is for customs monitoring of containers, and ISO17363 is for the purpose of supply chain management using readable RFID identification tags and freight tags on freight containers.

According to the energy supply method, RFID can be divided into passive RFID, active RFID, and semi-active RFID. Passive RFID has short reading and writing distance and low price; Active RFID can provide longer read and write distances, but it requires battery power and is costly, making it suitable for long-distance read and write applications. [2]  
Passive RFID products are the earliest, most mature, and widely used products in the market. For example, bus cards, cafeteria meal cards, bank cards, hotel access cards, second-generation ID cards, etc. It can be seen everywhere in our daily lives and belongs to the category of close contact identification. The main operating frequencies of the product are low frequency 125KHZ, high frequency 13.56MHz, ultra-high frequency 433MHz, and ultra-high frequency 915MHz.  
The development of active RFID products has been slow in recent years, and their long-distance automatic identification characteristics determine their huge application space and market potential. There are important applications in the field of remote automatic recognition, such as smart prisons, smart hospitals, smart parking lots, smart transportation, smart cities, smart earth, Internet of Things, etc. Active RFID has emerged as a rising star in this field and belongs to the category of long-range automatic identification. The main operating frequencies of the product are UHF 433MHz, microwave 2.45GHZ, and 5.8GHz

Radio Frequency Identification (RFID) technology, also known as Radio Frequency Identification, is a communication technology commonly known as electronic tags. Specific targets can be identified through radio signals, and relevant data can be read and written without establishing mechanical or optical contact between the identification system and the specific target.
Large data storage capacity. The capacity of one-dimensional barcodes is 50 bytes, the maximum capacity of two-dimensional barcodes can store 2 to 3000 characters, and the maximum capacity of RFID is a few megabytes. With the development of storage media, data capacity is also constantly expanding. The amount of information that future items will need to carry will continue to increase, and the demand for expanding the capacity of labels will also correspondingly increase.