Radio frequency identification devices (RFID) technology was born in the 1940s to the 1950s. It has developed so far. After the integration of a variety of emerging technologies, great changes have taken place in the form and application scope. Today’s RFID technology integrates Internet of things technology, wireless information and power transfer technology, object identification and energy efficient Sensing technology has been regarded as a new paradigm of sensing and communication in the future information system, and it is also regarded as one of the most potential information technologies in the 21st century. RFID technology has the characteristics of non-contact sensing, wireless information transmission, label wireless power supply, easy deployment, non line of sight transmission, flexible pasting and so on. It is the key technology of future IOT application and industrial manufacturing 4.0 (intelligent manufacturing, logistics, health care, agriculture, food supply chain).
This paper first introduces the development of RFID tag technology, and then summarizes the development of RFID antenna technology and new sensors in recent years. Then it gives a brief overview of the application of RFID frontier innovation in recent years. Finally, it describes the current challenges faced by RFID and makes prospects for the future development.
02. Development of RFID tag technology
2.1 chip less RFID
In the past, the common sense of RFID tags used to work in the way of inductive coupling and backscattering. In essence, their tags are integrated circuits with silicon chips. At present, in order to improve the convenience of RFID deployment and reduce the cost of deployment, people propose to use RFID tags without silicon chips, whose working mode is to change the radio wave shape of RFID tags to transmit data It doesn’t need complex integrated circuit, in essence, it works through circuit frequency resonance effect.
The data storage capacity of chip less RFID is far less than that of RFID system with chip. However, due to the absence of silicon chip, the cost of chip less RFID is significantly lower than that of chip RFID. Therefore, chip less RFID has become a competitive choice for low-cost sensing and identification applications.
2.2 RFID tag flexible and fast printing technology
Inkjet printing technology makes RFID tags more convenient to be manufactured and used. Printed electronic technology is a new technology that combines traditional printing technology with electronic technology and applies traditional printing technology to electronic manufacturing. Compared with the traditional manufacturing methods of electronic components, printing technology is more stable in the oxidation environment, and has the advantages of cost-effectiveness, flexibility and environmental friendliness. Among them, the contact type mainly includes flexographic printing, offset printing and screen gravure printing, and the non-contact type mainly includes inkjet printing.
Flexible RFID printing technology is mainly used to manufacture RFID antenna based on chip and RFID without chip. For RFID tag manufacturing, new tags print graphene, silver or copper nanoparticles on photo paper, plastics or textiles for circuit integration. In the past decade, the scarcity of resources, the rapid renewal of products and the deterioration of the ecological environment make the market put forward the requirements of low cost, flexibility and green for modern technology. As a kind of electronic substrate, paper substrate has the advantages of low cost and mass production. At the same time, although nano particle conductive ink is made of many materials (such as copper (Cu), gold (AU), graphene, carbon nanotubes (CNT)), silver nano particle ink is a new choice for electronic conductive trace of printing paper.
Through the use of new label printing technology, we can manufacture cheaper and better performance RFID tags.
2.3 RFID tag IC development
In RFID applications, many new RFID integrated circuits have been invented as RFID tags, including UHF EPC class-1 G2 and NFC ISO / iec14443 and ISO / IEC15693. Some representative integrated circuit technologies are summarized in Table 1.
Most of these integrated circuits integrate RF energy acquisition circuits, internal logic control and memory, and serial ports that allow read and write capabilities to update sensor data. Some RFID chips include analog-to-digital converters (ADCs) to interface with sensor components, such as mlx90129 and sl13a. Melexis optimizes mlx90129 for low-power, low-voltage battery and battery free applications. It can be used as an RFID thermometer with any other components; Sl13a tag meets the iso15693 standard and can be used with near field communication (nfc-v) and high frequency radio frequency identification (HF RFID) readers. AMS provides medical device OEMs with opportunities to realize some new applications. For example, the tag can be easily and safely implanted into patients (or directly swallowed by patients). Patients only need to put the mobile phone or tablet computer with RF function close to the body to read specific physiological values and master their physical condition all day long. Ti’s rf430frl152h RFID sensor integrates MSP430 and a / D (analog / digital) interface, which effectively promotes the further development of the chip. It has the comprehensive advantages of low power consumption, fast read / write speed, unlimited read / write durability and high electromagnetic immunity. It is composed of a substrate, an integrated antenna and ambient light and temperature sensors. The integration of built-in sensor modules makes the development of different RFID based applications more convenient.
03. RFID technology development and innovative application
3.1 development of RFID antenna technology
The RF energy acquisition circuit is mainly composed of antenna, rectifier, multiplier and energy storage device, as shown in the figure below
The antenna captures the RF energy in the electromagnetic field, and then the rectifier converts the RF energy into DC voltage through the rectifier. Finally, the voltage increased by the voltage multiplier is stored in the energy storage device.
The commonly used antennas are shown in the figure below. The antenna in figure a is usually used in HF RFID system, and the antenna in B-D is commonly used in UHF RFID system.
High gain antenna can improve the conversion efficiency and get more power, so high gain antenna is the first choice. The performance of antenna can be evaluated by gain, frequency band, radiation direction, polarization, physical size or application field.
The antenna is located in the front of the RFID sensor device, which is the key component to determine the performance of the RFID sensor, including the reading distance, working speed and the size of the sensor module. Therefore, the design of novel antenna to improve the performance of sensor equipment and adapt to different application scenarios has become a research hotspot. The main contributions are focused on size miniaturization, foldable antenna, 3D antenna, metal surface mount antenna, multi band antenna, omnidirectional and directional antenna, etc.
RFID sensor, a typical RFID tag antenna design is universal and requires impedance matching for the maximum reading range. However, due to the emergence of sensors and various devices, energy consumption is greatly increased. In order to obtain stable RFID sensor data, the RFID sensor antenna can also be configured as a multi port to collect natural energy to enhance the energy collection of self powered wireless sensor.
3.2 RFID innovative sensor development
Because RFID sensor technology has huge business opportunities in the future era of Internet of things, some industry pioneers including Ti, STMicroelectronics, ASM, farsen, axzon and Impinj have also invested a lot of energy in this specific field. Some novel RF-DC converter modules, RFID transceivers and RFID integrated circuits have been invented. There are also some new technology solutions for different applications on the market.
On the basis of RFID integrated circuit, these companies also give some new application module examples.
In (a) above, the sps1m002 series produced by on semiconductor uses magnuss2 integrated circuit. The sensor label is designed for passive sensing of moisture on various surfaces and finished products (such as plastic, wood and gypsum). The tag digitizes the humidity detection / liquid level information, which can be read by UHF RFID Gen 2 standard reader. This battery free wireless sensor can greatly improve the reliability of the final product and provide many benefits for deployment in an industrial environment. Figure (b) is the EPC C1G2 tag manufactured by farsens company. Zygos-rm can customize different antenna designs and sizes according to specific applications. It is used for load sensing. The load range is 0 ~ 5kg, the accuracy is 50g, and the sensing distance of sensor limit is 20m. Figure (c) shows a passive RFID temperature sensor with high accuracy (error less than 0.1 ℃) produced by Texas Instruments (TI), with sensing range of – 40 ℃ – 85 ℃. It can be used, for example, to detect changes in the temperature of a person’s skin, so as to understand the state of a person’s health. Figure (d) shows the NFC keyboard produced by Texas Instruments Corporation (TI) to replace the touch keyboard. The keyboard can input more than 400 characters per minute, has no battery, and has low power consumption (the power consumption of MSP430 MCU and rf430cl330 RFID tag is about 20 MW). Mobile phones supporting NFC can quickly find and recognize the keyboard.
04. New applications based on RFID sensor
RFID sensor technology integrates wireless power, data transmission and target recognition. It is a new way of sensing and communication, and has a wide application prospect. On the one hand, wireless power supply and data transmission provide an interface that can transmit sensor data from the measured object without wires and batteries, which makes the sensor equipment greatly miniaturized. Therefore, with the new integration of RFID technology and lightweight sensor technology, some challenging measurement tasks in the past become more convenient. The application fields include consumer electronics, health care, food and agriculture, chemical industry, manufacturing and logistics, civil engineering, automobile, machinery, etc.
05. Challenges and trends
5.1 current challenges of RFID
Although we have made continuous progress in technology and found many innovative applications of RFID based sensor technology through literature research, most of the work is still in the stage of proof of concept demonstration and laboratory testing and evaluation. There is a big gap between the research results and practical application. The main challenges are as follows:
1) The efficiency of energy acquisition and power conversion of RF front-end;
2) The basic technology of RFID sensor shows great heterogeneity in antenna, integrated circuit function, sensor element and data protocol;
3) Performance reliability, RFID sensor is mainly attached to the measured object for identification and parameter sensing. However, in practical application, it will also be affected by some environmental factors;
5.2 RFID development trend
On the one hand, how to integrate some new materials and new processes to improve the performance of RFID sensor technology will become the focus of research. RFID relay technology used to expand the reading range of RFID sensors will also be very meaningful. In addition, RFID sensor networks for wide area and multi-target monitoring will also occupy a place in academic research by using battery free and lightweight performance.
On the other hand, RFID sensor technology is considered to be the revolutionary technology of information system in the future, and its application of Internet of things has received special attention. These include but are not limited to:
1) Product life cycle management (PLM) in manufacturing industry;
2) Continuous monitoring of human physical characteristics;
3) RFID sensor in intelligent logistics;
4) RFID sensor in intelligent agriculture;
With the rapid development and wide application of RFID sensor technology, new solutions have been produced in different application fields, which has a very broad prospect for the rich sensor applications of Internet of things in the future. In the era of Internet of things, RFID sensor technology will continue to attract the research of industry and academia, and sensor and communication will become the foundation of information infrastructure. RFID sensor technology will have more applications in the biomedical field, which can be implanted into the human body. In civil engineering, it will be integrated into civil structure for health monitoring, and in safety production for low-cost and high-quality monitoring. It will have a more profound impact in many fields.