RFID
RFID is the abbreviation for Radio Frequency Identification, that is, radio frequency identification technology, commonly known as electronic tags.
What is RFID technology?
RFID radio frequency identification is a non-contact automatic identification technology, it through the radio frequency signal automatically identify the target object and obtain the relevant data, identification work without human intervention, can work in a variety of harsh environments. RFID technology can identify high-speed movement objects and can identify multiple tags at the same time, the operation of the fast and convenient.
Ferguson, chief scientist at Accenture Laboratories, believes that RFID is a breakthrough technology: "First, you can identify a single very specific object, rather than bar codes that can only identify a class of objects; second, its use of radio frequency, can be read through the external material data, while the bar code must rely on the laser to read the information; third, you can read multiple objects at the same time! Third, multiple objects can be read at the same time, while the bar code can only be read one by one. In addition, the amount of information stored is very large."
What are the basic components of RFID?
The most basic RFID system consists of three parts:
Hashtag (Tag): by the coupling element and the chip, each tag has a unique electronic code, attached to the object to identify the target object;
Reader (Reader): read (and sometimes write) tag information device, can be designed as a hand-held or fixed type;
Antenna (Antenna): between the label and the reader to transmit radio frequency signals.
A complete system also needs to have: data transmission and processing system.
What is the basic working principle of RFID technology?
The basic working principle of RFID technology is not complicated: the tag enters the magnetic field, receives the radio frequency signal from the decoder, and sends out the product information stored in the chip by virtue of the energy gained from the inductive current (Passive Tag, passive tag or passive tag), or actively sends out a certain frequency signal (Active Tag, active tag or active tag); The decoder reads the information and decodes it, then sends it to a centralized information system for relevant data processing.
What is RFID middleware?
RFID is one of the top 10 strategic technologies that organizations are advised to consider introducing in 2005, and middleware can be described as the backbone of RFID operations because it accelerates the introduction of critical applications.
The RFID industry has unlimited potential, with applications in manufacturing, logistics, healthcare, transportation, retail, defense, etc. Gartner Group believes that RFID is one of the top ten strategic technologies that companies can consider introducing in 2005, but the key to its success is the availability of key components in addition to the price of the tag, the antenna design, the standardization of the bands, and certification of the equipment. However, the key to its success, in addition to the price of tags (Tag), antenna design, standardization of bands, equipment certification, the most important thing is to have a key application software (Killer Application), in order to quickly promote. And the middleware (Middleware) can be called the RFID operation of the center, because it can accelerate the key application of the introduction.
What makes retailers so excited about RFID?
Retail analysts at Sanford C. Bernstein & Co. estimate that Wal-Mart could save $8.35 billion a year by adopting RFID, much of it due to labor savings from not having to manually look at incoming bar codes. While some other analysts think the $8 billion figure is overly optimistic, there's no doubt that RFID could help solve two of the retail industry's biggest challenges: merchandise out-of-stocks and shrinkage (lost product due to theft and supply chain disruptions), and right now Wal-Mart loses almost $2 billion a year on theft alone, which would put a legitimate business with that kind of turnover in the 694th on the list of America's 1000 largest companies. Research organizations estimate that this RFID technology could help reduce theft and inventory levels by 25 percent.
What are the typical applications of RFID technology?
Logistics and supply management
Manufacturing and assembly
Airline baggage handling
Mail/express parcel handling
Document tracking/library management
Animal identification
Sports timing
Access control/electronic tickets
Automated road pricing
Passive RFID tag structure and working principle
Passive RFID tags themselves do not carry batteries, relying on the electromagnetic energy sent by the reader to work. Because of its simple structure, economical and practical, and therefore widely used. Passive RFID tags are composed of RFID IC, resonant capacitor C and antenna L. The antenna and capacitor form a resonant circuit, tuned to the carrier frequency in the reader to obtain the best performance.
Many manufacturers follow the International Telecommunication Union's specifications, there are six kinds of RFID frequency, respectively, 135KHz, 13.56MHz, 43.3-92MHz, 860-930MHz (i.e., UHF), 2.45GHz, as well as 5.8GHz. passive RFID is mainly used in the first two kinds of frequency.
RFID tag structure
RFID tag antenna has two kinds of antenna form: (1) wire-wound inductive antenna; (2) in the dielectric substrate embossed or printed engraved corrosion of the disk spiral antenna. Antenna form by the carrier frequency, tag package form, performance and assembly costs and other factors.
After selecting the antenna, the next step is how to attach the silicon IC to the antenna. there are also two basic methods for IC attachment: (1) using chip-on-board (COB); (2) the bare chip is directly attached to the antenna. The former is commonly used for wire-wound antennas; while the latter is used for etched antennas.CIB is a resonant capacitor and RFID IC packaged together in the same housing, and the antenna is connected to the two external terminals of the COB with a soldering iron or fusion soldering process. Since most COBs are used for ISO cards, a type of card that meets the ISO standard thickness (0.76) specifications, the typical thickness of a COB is about 0.4 mm. Two common forms of COB packages are the IOA2 (MOA2) used by IST and World II used by U.S. company HEI.
Bare chip direct bonding reduces intermediate steps and is widely used for low-cost and high-volume applications. There are also two methods available for direct bonding, (1) lead soldering and (2) flip-flop process. When using the flip-flop process, the chip pads need to make a specialized solder ball, the material is gold, the height of about 25祄, and then the solder ball flip-flop in the antenna's printed alignment. The lead soldering process is simpler, the bare chip is directly soldered to the antenna with leads, and the soldering area is then sealed with black epoxy resin. For low volume production, this process is less expensive; for high volume production, a flip-flop process is preferred.
Basic principle of operation
Wireless RFID tag performance by the tag size, modulation form, circuit Q, device power consumption, and the depth of modulation greatly affected. The following is a brief description of how it works.
The RFID IC is equipped with a 154-bit memory to store the tag data, and there is also a very low on-resistance modulation gate controller (CMOS) inside the IC, which operates at a certain frequency. When the reader transmits an electromagnetic wave, so that the tag antenna inductive voltage reaches VPP, the device works to send data back in Manchester format.
The data sending is done by tuning and de-tuning the external resonant loop. The process is as follows: when the data is logic high, the gate controller cuts off, tuning the tuning circuit to the intercept frequency of the reader, which is the tuned state, and the sense voltage reaches its maximum value. Carried out in this way, tuning and de-tuning in the tag coil to produce an amplitude modulation signal, the reader detects the voltage waveform envelope, you can reconstruct the data signal from the tag.
The switching frequency of the gated tube is 70 KHz, and it takes about 2.2 ms to complete all 154 bits of data. after sending all the data, the device enters a 100 ms sleep mode. When a tag enters sleep mode, the reader can read data from other tags without any data conflict. Of course, this function is affected by the following factors: the distance from the tag to the reader, the orientation of the two, the movement of the tag, and the spatial distribution of the tags.
Design Example
The MCRF 355/360 are 13.56MHz devices from Microchip. The 355 can be used for both COB and direct attach, while the 360 has an internal 100pf capacitor and requires only an external inductor. The device sends data with nearly 100% modulation, and the depth of modulation determines how the tag's coil voltage changes from "high" to "low," i.e., distinguishing between tuned and de-tuned states.
External component values are usually optimized at one-third to one-half. For example, if the inductor coil is 3 turns between antenna A and antenna B, it is 1 turn between antenna B and the VSS. When the MCRF 355 is fabricated as a COB, two identical 68Pf capacitors are built in series. Capacitor C1 is connected between antenna A to antenna B and C2 is between antenna B to VSS.
In order to achieve the designed performance, the tag should be accurately tuned at the carrier frequency of the reader. However, there will always be deviations in the components used, causing variations in the read distance. Inductance error can be controlled within 1~2%, so the read distance is mainly caused by capacitance error. External capacitors should have an error of 5% or less and a Q value greater than 100. The MCRF360R's internal capacitors are made of silicon oxide and have an error of 5% or less on the same silicon wafer, while different batches have an error of about 10%.
The memory data of MCRF355/360 can be programmed in the factory or in the field with a contact programmer.
RFID operating frequency guide and typical applications (1)
Different frequency bands of RFID products will have different characteristics, this article describes in detail the passive sensor in the different operating frequencies of the product characteristics and the main applications.
Currently the definition of RFID products operating frequency has a low-frequency, high-frequency and very high-frequency frequency range in line with different standards of different products, and different frequency bands of RFID products will have different characteristics. One of the inductor has a passive and active two ways, the following details of the passive inductor in different operating frequencies and the characteristics of the product and the main applications.
A, low frequency (from 125KHz to 134KHz)
In fact, RFID technology is first widely used in low-frequency applications and promotion. The frequency is mainly through the inductive coupling way to work, that is, in the reader coil and inductor coil between the existence of transformer coupling. The voltage induced in the inductor antenna by the alternating field of the reader is rectified and can be used as the supply voltage. The magnetic field region can be well defined, but the field strength drops too quickly.
Characteristics:
1. The general operating frequency of inductors working at low frequency is from 120KHz to 134KHz, and the TI's operating frequency is 134.2KHz. The wavelength of this band is about 2500m.
2. The general low frequency is able to pass through items of any material without decreasing the reading distance except for the influence of metal materials.
3. There are no special licensing restrictions worldwide for readers operating at low frequencies.
4. Low-frequency products are available in different packages. A good package form is too expensive, but has a service life of more than 10 years.
5. Although the magnetic field area drops off quickly at this frequency, it is able to produce a relatively uniform read/write area.
6. Relative to other frequency bands of RFID products, the band data transfer rate is relatively slow.
7. The price of the inductor is relatively expensive compared to other frequency bands.
Main applications:
1. Livestock management system
2. Automobile anti-theft and keyless door opening system
3. Marathon running system
4. Automatic parking lot fees and vehicle management system
5. Automatic refueling system applications
6. Hotel locking system applications
7. Application of hotel locking system
7. Access control and security management system
International standards in line with:
a) ISO 11784 RFID animal husbandry applications - coding structure
b) ISO 11785 RFID animal husbandry applications - technical theory
c) ISO 14223-1 RFID Livestock Applications-Air Interface
d) ISO 14223-2 RFID Livestock Applications-Protocol Definitions
e) ISO 18000-2 Defining Physical Layer, Impact Prevention, and Communication Protocols for Low Frequency
f) DIN 30745 Primarily a European standard defining waste management applications
II. High Frequency (Operating Frequency 13.56MHz)
Inductors at this frequency no longer require coils to be wound, and antennas can be made by corrosion alive printing. Inductors generally work by means of load modulation. That is, through the inductor on the load resistor on and off to prompt the reader antenna voltage change, realize the remote sensor on the antenna voltage amplitude modulation. The data can be transmitted from the inductor to the reader if the load voltage is turned on and off by data control.
Characteristics:
1. The operating frequency is 13.56MHz, and the wavelength of this frequency is roughly 22m.
2. The wavelength of this frequency passes through most materials except metal, but tends to reduce the reading distance. The sensor needs to be some distance away from the metal.
3. This frequency band is recognized worldwide and has no special restrictions.
4. The sensor is usually in the form of an electronic tag.
5. Although the frequency of the magnetic field area falls quickly, but can produce relatively uniform read and write area.
6. The system has anti-collision characteristics and can read multiple electronic tags at the same time.
7. Some data information can be written into the label.
8. The data transmission rate is faster than low frequency and not very expensive.
Main applications:
1. Application of library management system
2. Management of gas cylinders
3. Management and application of garment production line and logistics system
4. Three-meter pre-fee system
5. Management and application of hotel locks
6. Large-scale conference personnel access system
7. Fixed assets and other assets, such as the use of the Internet and the Internet.
7. Fixed asset management system
8. Management and application of pharmaceutical logistics system
9. Intelligent shelf management
International standards in line with:
a) ISO/IEC 14443 close-coupled IC card, the maximum reading distance of 10cm.
b) ISO/IEC 15693 sparse-coupled IC card, the maximum reading distance of 10 cm.
b) ISO/IEC 15693 sparse-coupled IC card, the maximum reading distance of 10 cm.
b) ISO/IEC 15693 Sparsely coupled IC cards, with a maximum read distance of 1m.
c) ISO/IEC 18000-3 This standard defines the physical layer of the 13.56MHz system, the anti-collision algorithms, and the communication protocols.
d) 13.56MHz ISM Band Class 1 This defines the interface definition for 13.56MHz compliance with EPC.
Three, VHF (operating between 860MHz and 960MHz)
VHF systems transmit energy through an electric field. The energy of the electric field does not fall very quickly, but the reading area is not very well defined. The frequency band reading distance is relatively far, passive up to about 10m. It is mainly realized by capacitive coupling.
Characteristics:
1. In this band, the global definition is not very the same - Europe and part of the Asian definition of the frequency of 868MHz, the North American definition of the frequency band for the 902 to 905MHz between, in Japan, the proposed frequency band for the 950 to 956 between. The wavelength of this band is about 30cm.
2. Currently, the power output of this band is currently defined uniformly (4W in the US and 500mW in Europe). Possibly the European limit will rise to 2W EIRP.
3. VHF band waves can not pass through many materials, especially water, dust, fog and other suspended particles material. Relative to the high frequency electronic tags, the frequency band electronic tags do not need to be separated from the metal.
4. The antenna of the electronic label is generally long and label-like. Antennas have linear and circular polarization two designs to meet the needs of different applications.
5. The band has good reading distance, but it is difficult to define the reading area.
6. There is a very high data transmission rate, in a very short time can read a large number of electronic tags.
Main applications:
1. supply chain management and application
2. production line automation management and application
3. air parcel management and application
4. container management and application
5. railroad parcel management and application
6. Logistics management system application
7.
International Standards:
a) ISO/IEC 18000-6 defines the physical layer of VHF and the communication protocol; the air interface defines two parts, Type A and Type B; and supports readable and writable operations.
b) EPCglobal defines the structure of the Electronic Article Code (EAC) and the VHF air interface and protocols for communication. Examples include Class 0, Class 1, UHF Gen2.
c) Ubiquitous ID Japanese organization that defines the UID coding structure and communication management protocol.
In the future, VHF products will be heavily used. For example WalMart, Tesco, the U.S. Department of Defense and Metro Supermarkets will all apply RFID technology in their supply chains.
Four, active RFID technology (2.45GHz, 5.8G)
Active RFID with low transmitter power, long communication distance, transmission of large amounts of data, high reliability and compatibility, etc., and passive RFID compared to the technological advantages are very obvious. It is widely used in highway toll collection, harbor freight management and other applications.
RFID system
RFID system
Automatic identification system composed of radio frequency tags, readers and computer networks. Usually, the reader in a region to transmit energy to form an electromagnetic field, radio frequency tags pass through the region when the reader's signal is detected to send the stored data, the reader receives the signal sent by the radio frequency tags, decoding and checking the accuracy of the data in order to achieve the purpose of identification.