The study of RFID knowledge

* Some of the information comes from our PhD's PPT, partly from the Web and others ' papers.

* The textbook we use is the Smart Card Technology (fourth edition)--ic card, RFID tag and Internet of Things (Tsinghua University computer series textbook) published by Tsinghua University Press (Wang Aiying)

* I just sorted out the contents below

Radio Frequency Identification Technology

Radio Frequency Identification (Radio Frequency identification, RFID) technology is a contactless automatic identification technology that uses RF signals through spatial coupling (inductive or electromagnetic coupling) or radar reflection transmission characteristics, to achieve contactless information transmission and through the transmission of information to achieve identification purposes . Radio frequency Identification technology is the most widely used in China is the RFID card.

extension of common automatic recognition methods and techniques include: optical symbol recognition technology, speech recognition technology, biometric identification technology, IC card technology, barcode technology and RFID RF technology.

RFID than other technology obvious advantage is that the electronic label and reader without contact to complete the identification.

Smart card (IC card)

Smart Card ("smart card"), also known as an integrated circuit card (Integrated circuit card, i.e. IC cards). It generally refers to the integrated circuit chip embedded in plastic and other substrates made of cards, shape and magnetic card similar to the chip has storage, encryption and data processing and other functions. Now, IC card products have entered into the financial, telecommunications, transportation, medical, identification and other fields.

According to the different reading and writing methods, IC card can be divided into contact IC card and contactless IC card. Both types of IC cards are sealed in the plastic card substrate inside, can be waterproof, dustproof, anti-magnetic. The surface of the contact IC card can be seen with a square gold plated interface with eight or six gold plated contacts for contact with the reader and read-write through the current signal. Contactless IC Card In addition to the card contains IC card circuit, also contains the relevant RF transceiver circuit and antenna coil. IC card can receive the signal of reader and writer in a certain distance, and realize non-contact reading and writing.

RF Identification Card

Radio Frequency identification card (RF card, RFID card), also known as contactless IC card (contactless Smart card) or contactless IC card, contactless card, induction card. Can be widely used in logistics, personal identification, intelligent parking, access control systems, anti-counterfeiting systems and production process controls and many other radio frequency identification systems.

Advantages of RFID Cards

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Application of RFID Card

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RFID system

The RFID system consists of five components, including: transmitter, receiver, microprocessor, antenna, label. Conveyors, receivers, and microprocessors are often packaged together and collectively referred to as readers, so industry often divides RFID systems into readers (reader), antennas (antenna), and labels (TAG) three major components.

• Reader: The device that reads or reads/writes the electronic tag information, the main task is to control the RF module to transmit the reading signal to the label, and receive the response of the label, decode the object identification information of the label, and transmit the other related information of the object identification information and tag to the host for processing.
• Antenna: A transmitting and receiving device for transmitting data between a label and a reader.
• Electronic label (or RFID tag, transponder): consists of a chip and a built-in antenna. The electronic data in a certain format is stored in the chip, which is the real data carrier of the RFID system as the identification information of the object to be identified. The built-in antennas are used to communicate with the RF antennas.

Working principle

After the electronic label enters the antenna magnetic field, if receives the reader the special radio frequency signal, can rely on the current to obtain the energy to send out the product information stored in the chip (the passive label), or the active transmission certain frequency signal (has the source tag), the reader reads the information and decodes, Sent to the central information system for data processing.

Work flow

1. The reader transmits a certain frequency RF signal through the transmitting antenna ;

2. When the RF card enters the working area of the transmitting antenna, the induced current is generated and the RF card gets the energy activated ;

3. The RF card will send out the information of its own encoding via the internal sending antenna of the card;

4. The system receiving antenna receives the carrier signal from the RF Mehsud, which is transmitted to the reader by the antenna regulator, and the reader is demodulated and decoded to the receiving signal, and then sent to the background main system for related processing;

5. The main system according to the logic operation to determine the legitimacy of the card, for different settings to make corresponding processing and control, issued a command signal control actuator action .

Coupling of RF signals

There are two types of RF signal coupling between the reader and the electronic tag:
(Ⅰ) inductance coupling. The transformer model, through the space high frequency alternating magnetic field realizes the coupling, is based on the electromagnetic induction law.
(Ⅱ) Electromagnetic backscatter coupling. The radar principle model, the emitted electromagnetic wave, touches the target to reflect, simultaneously carries back the target information, is based on the electromagnetic wave space propagation law.

	Inductive coupling	Electromagnetic Inverse scattering coupling
Model	Transformer model	Radar principle Model
Principle	Law of electromagnetic induction	The spatial propagation law of electromagnetic waves
Typical working distance	10~20cm	3~10m
Typical operating frequency	125kHz, 225kHz, 13.56MHz	433MHz, 915MHz, 2.45GHz, 5.8GHz
Label	Typical low frequency, high frequency labels with ring antennas	UHF and microwave labels with bipolar antennas

Two kinds of modulation methods for the two coupling modes are load modulation and reverse scattering modulation.

RFID frequency

RFID frequency is an important parameter index of RFID system, which determines the factors such as working principle, communication distance, equipment cost, antenna shape and application field. The typical operating frequency of RFID is 125KHz, 133KHz, 13.56MHz, 27.12MHz, 433MHz, 860-960mhz, 2.45GHz, 5.8GHz and so on. According to the operating frequency, the RFID system is concentrated in three regions of low frequency , High frequency and UHF .

The higher the frequency, the farther the transmission distance, but the diffraction or penetrating ability is weaker.

dual frequency label and dual frequency system

The high frequency and low frequency strengths are designed to identify dual-band products that are far and penetrating and can be used for animal identification, interference with conductor materials, and humid environments.

Dual-frequency RFID system is mainly used for distance requirements, multi-card recognition and high-speed identification occasions, such as: supply chain management, personnel flow tracking, animal tracking and identification, mining operations and underground network management and sports timing.

China RFID the frequency band planning

UHF band RFID technology has the characteristics of good wave propagation, moderate label size, suitable for long-distance identification and large-scale application, so has been the focus of the industry.

Each country has different frequency planning and usage in this band (the UHF used in Europe is 865~868mhz, the United States is 902~928mhz, and Japan is 952mhz~954mhz), but all are concentrated in the 860~960mhz range.

China UHF band trial Use frequency Rate of 840~845mhz and the 920~925mhz.

Classification of radio Frequency Identification system

The distance between the label and Reader in the RFID system is an important index in the application of radio frequency identification system. Depending on the distance, the coupling between the label antenna and the reader can be divided into three categories: the dense coupling system, the remote coupling system and the long distance system.

(1) Dense coupling system

The typical distance range of a dense coupled system is 0~1cm. There is an inductive coupling between the label of the coupling system and the reader. Its operating frequency is generally below 30MHz.

(2) Remote Coupling system

The typical distance of a remote coupling system can reach 1m. The remote coupling system can be subdivided into the near coupled system and the hydrophobic coupling system, the former has a typical distance of 15cm and the latter is 1m. All remote coupling systems are inductively coupled between the reader and the label. The typical operating frequency of a remote-coupled system is 13.56MHz, and there are other frequencies, such as 6.75mhz,27.125mhz or under 135kHz.

The next Post's experiment is a near-coupled system, I have a rough measurement of the communication distance is about 4cm, the operating frequency is 13.56MHz

(3) Long distance system

The typical action distance of a long distance system is 1~10m, and the individual systems also have farther function distances. Both the reader and the label of all the long-range systems are coupled with electromagnetic backscatter. Long-distance systems are used in the microwave range of electromagnetic wave work, the frequency of transmission is usually 2.45GHz, but also the frequency of the system is 5.8GHz and 24.125GHz.

Other Related technologies

• Energy Transfer

The transfer of energy between the reader and the RFID card is based on the principle of the coupling transformer.

• Data transfer

1. Signal modulation
2. Data encoding

Load tuning, using data signals to digitally adjust the load on the card.

Common digital modulation techniques include amplitude keying (amplitude shift keying,ask), frequency shift keying (Frequency shift KEYING,FSK), and phase shift keying (Phase shift KEYING,PSK). ASK and PSK are more commonly used.

Data encoding, on the one hand to facilitate data transmission, on the other hand can be transmitted data encryption.

The coding methods commonly used in radio frequency identification systems are: NRZ encoding (Non-return-to-zero), Manchester Code (Manchester), unipolar Zero Encoding, Miller Code (Miller), modified Miller Coding, differential bidirectional encoding, differential coding.

• Data integrity

1. Check
2. Multi-channel access

The most commonly used verification methods in radio frequency identification are parity, cyclic redundancy check (CRC), and longitudinal redundancy check.

When radio frequency identification systems work, there are two basic types of communication: Communication from the reader to the label and communication from the tag to the reader.

The multiple access methods in radio communication system are basically the following: Air Division Multiplexing (SCDMA), Time Division Multiplexing (TDMA), Frequency Division Multiplexing (FDMA), Code Division Multiplexing (CDMA). In the radio frequency Identification System, the general use is TDMA.

Anti-collision algorithm, frame-based time slot Aloha protocol, Q Protocol, random binary Tree protocol and query binary tree protocol.

• Data security

1. Identification of mutual symmetry
2. Encrypted data transfer

Technical details can be downloaded to the end of the text of our PhD ppt, combined with the textbook study seriously.

Near-coupled IC card--mifare 1

The current market is more widely used is the carrier frequency of 13.56MHz, working distance in the 2.5~10cm of the near-coupled IC card, the International standard is ISO/IEC 14443.

Philips is the first company in the world to develop RFID cards, and its Mifare technology has been developed as an international standard for Is0/iec 14443 TYPE A.

Features of the Mifare 1 card

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Mifare 1 CHIP logic structure

Mifare 1 chip internal structure is more complex, can be divided into RF interface, digital processing unit, EEPROM three parts:

1. RF interface: In the RF RF interface circuit, including the waveform conversion module. It can receive 13.56MHZ radio modulation frequency on the reader, on the one hand the modulation/demodulation module, on the other hand waveform conversion, and then the rectification of the filter, and then the voltage regulator and other further processing, the final output of the circuit work on the card.
2. Anti-collision module: If there are multiple Mifare 1 cards within the operating range of the reader's antenna, the conflict prevention feature of the anti-collision module will be activated: Select a card according to the card's serial number. The selected card will be exchanged directly with the reader, the unselected card is waiting and ready to communicate with the reader.
3. Authentication module: After a card is selected, any action on the card storage area must be authenticated, and only the data block can be accessed by a password check. Mifare 1 Card has 16 sectors, each sector can be set their own password, non-interference. Therefore, each sector can be applied independently in one application. The entire card can be designed to be used as a "one-card" form.
4. Control and Arithmetic unit: This unit is the control center of the whole card, and is the "brain" of the card. It mainly carries on the micro-operation control to each unit of the whole card, coordinates each step of the card, also carries on the arithmetic operation processing to the various collect/send data, the CRC computation processing and so on.
5. EEPROM interface: connected to EEPROM.
6. Encryption unit: Mifare's CRYPTO1 data stream encryption algorithm will guarantee the data security when the card communicates with the reader.
7. eeprom:1k bytes, divided into 16 sectors. 4 blocks per sector, 16 bytes per block.

Memory structure and read-write control

The following will not write, this section of the PPT I did not, not enough of our doctor, this knowledge is also very important.

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The End

Next blog post I'll write a simple RFID experiment based on Arduino, which is the basis for completing our PhD's experimental report.

Finally, I enclose some information related to this article:

mf_rc522 Chinese information. pdf
Mf1_s50.pdf
MF1_S50 Introduction (Chinese). pdf
Design and application of rc500_ RFID card reading and writing module. pdf
Seventh-Radio Frequency Identification Technology fundamentals (IC card and RFID tag) 1--20151027.ppt
Seventh-Radio Frequency Identification Technology fundamentals (IC card and RFID tag) 2--20151027.ppt

The study of RFID knowledge