Radio Frequency Identification Technology Radio frequency identification technology (RFID) is a non-contact automatic identification technology. Its basic principle is to use radio frequency signals and spatial electromagnetic coupling transmission characteristics to realize automatic recognition of the identified objects. Radio frequency identification systems generally consist of two parts, namely contactless IC cards (transponder tags) and readers (reader readers). In the practical application of radio frequency identification, the non-contact IC card is attached to the recognized object. When the non-contact IC card passes its readable range, the reader automatically sets the convention in the non-contact IC card in a non-contact manner. The identification information is taken out, so as to realize the function of automatically identifying the article or automatically collecting the article flag information. Classification of Radio Frequency Identification Technology According to the contactless IC card power supply form can be divided into two kinds of active systems and passive systems. The active radio frequency non-contact IC card uses the energy of the battery in the non-contact IC card, and the recognition distance is long, reaching several tens of meters or even hundreds of meters, but its lifetime is limited and the price is high. The passive RF non-contact IC card does not contain a battery. The energy of the electromagnetic field emitted by the coupled reader is used as its own energy. The recognition distance is short, generally a few centimeters to several tens of centimeters. It is lightweight, small in size, and has a long life. Cheap, you can make a variety of thin cards or button cards. According to the non-contact IC card operating frequency can be divided into low frequency, high frequency and ultra-high frequency and microwave systems. The low frequency system generally works at 100-500kHz. The common operating frequency is 125kHz and 134.2kHz. The high frequency system operates between 10-15MHz. The common high frequency operating frequency is 13.56MHz; the UHF operating frequency is 850- 960MHz, common UHF operating frequency is 915MHz; microwave works in the microwave section of 2.4-5GHz. Low-frequency systems are used in small data applications; high-frequency systems are used in applications that transfer large amounts of data; UHF systems are used in applications that require long read and write distances and high read and write speeds. According to the read/write capability of the non-contact IC card, it is divided into read-only and read-write. The read-only non-contact IC card has only read-only memory (ReadOnlyMemory, ROM). The ROM is used to store programs and data. The information cannot be changed and can only be output. The internal memory of the readable and writable contactless IC card is composed of EEPROM or FLASH (Electrically Erasable Memory). This kind of memory is powered on. Next, you can erase the original data and rewrite the data. Basic principles of radio frequency identification technology Radio frequency identification technology involves many fields. There are multiple technical solutions. We use the Type B non-contact IC card technology solution with 13.56 MHz operating frequency and conforming to the ISO14443 international standard as an example to describe the basic architecture and principle of the radio frequency identification system. In order to read or write data, data must be transferred between the contactless IC card and the reader. The non-contact IC card and the reader construct the basic principle transmission channel of the non-contact wireless radio frequency identification technology between the two through their respective antennas. Data transmission uses a half-duplex method, that is, the data transmission from the non-contact IC card to the reader is alternated with the data transmission from the reader to the non-contact IC card. 1, non-contact IC card energy supply Non-contact IC cards use an electronic data carrier, usually consisting of a single microchip and large area coils used as antennas. On this data carrier, the amount of data stored can reach several thousand bytes. Non-contact IC cards are almost all passive. This means that all the energy needed for microchip operation must be supplied by the reader. The high frequency, strong electromagnetic field is generated by the reader's antenna coil, which passes through the non-contact IC card coil cross-section and the space around the coil. We can treat the electromagnetic field between the contactless IC card and the antenna of the reader as a simple alternating magnetic field. A small part of the magnetic field of the magnetic field passes through a non-contact IC card antenna coil at a certain distance from the antenna coil of the reader, and inductively generates a non-contact IC card power supply voltage Ui on the non-contact IC card antenna coil. This is rectified to serve as a power source for the data carrier (microchip). A capacitor Cr is connected in parallel with the antenna coil of the reader to form a parallel resonant circuit, which adjusts the resonant frequency of the circuit to 13.56 MHz. When the loop is in resonance, the reader antenna coil generates a very large current. This method can be used to generate the field strength required for the operation of a long-distance non-contact IC card. The antenna coil and capacitance C1 of the non-contact IC card constitute an oscillation loop and are tuned to the transmitter's transmission frequency. With this loop resonance, the voltage U on the non-contact IC card coil reaches a maximum value. The structure of the two coils can also be interpreted as a transformer (coupling of transformers), and there is only a very weak coupling between the two coils of the transformer. The power transmission efficiency between the reader's antenna coil and the non-contact IC card and the operating frequency and the number of turns of the non-contact IC card coil, the area surrounded by the non-contact IC card coil, the relative angles of the two coils, and the angle between them Distance is proportional. 2, non-contact IC card to reader data transmission If the non-contact IC card is placed in the alternating magnetic field of the reader antenna, the non-contact IC card takes energy from the magnetic field. The radio frequency circuit in the reader can measure the additional power consumption of the non-contact IC card through the voltage drop in the circuit internal resistance Ri. The turning on and off of the load resistor on the non-contact IC card antenna causes the voltage on the reader antenna to change, enabling the amplitude modulation of the reader antenna voltage with a long-distance non-contact IC card. If people control the turn-on and turn-off of the load voltage through data, then these data can be transmitted from the non-contact IC card to the reader. This data transmission method is called load modulation. Since the coupling between the reader antenna and the non-contact IC card antenna is weak, the voltage fluctuation of the reader antenna indicating the useful signal is smaller than the output voltage of the reader in an order of magnitude. In practice, for a 13.56 MHz system, when the reader's antenna voltage is 100V, only about 10mV of useful signal can be obtained. Detecting these small voltage changes requires a huge overhead on the circuit. To solve this problem, people use the modulation wavebands generated by voltage amplitude modulation of non-contact IC card antennas. If the non-contact IC card's additional load resistance is turned on or off at a high clock frequency fh, then two spectral lines are generated at a reader transmission frequency +/-fh distance, which are easily detectable. This new frequency is called a subcarrier. By using the load modulation of the subcarriers, two modulation wavebands can be generated on the reader antenna at both sides of the operating frequency of 13.56 MHz. With a bandpass filter at one of two frequencies 13.56+/-fh, these two modulated wavebands can be separated from the reader's stronger signal and after amplification, the subcarrier signal can be easily demodulated. . 3, data transmission protocols and methods The mutual communication between the reader and the non-contact IC card is initiated by the reader. The reader first encodes the signal to generate a baseband coded signal, and then modulates the coded signal to a transmit frequency of 13.56 MHz and transmits the signal through the antenna; non-contact IC The card antenna receives the 13.56 MHz carrier signal, and the demodulator demodulates the baseband encoded signal from the carrier frequency. The 3 data transmission protocol and the decoding circuit recover the original information from the baseband encoded signal. In the TypeB contactless card system, encoding and modulation are performed as specified in Table 1. 4, data integrity When using non-contact card technology to transmit data, it is easy to encounter interference, so that the transmission data changes to cause transmission errors. Data troubleshooting and error correction algorithms are often used to solve this problem. Frequently used methods include parity check, longitudinal redundancy check, and cyclic redundancy check. These methods are used to identify transmission errors and initiate corrective actions, or to discard erroneously transmitted data, or to retransmit erroneous data blocks. When the RFID system is working, multiple non-contact IC cards may exist simultaneously within the scope of the reader. In order to prevent the non-contact IC card data from colliding with each other and cannot be read out, the reader will start the anti-collision mechanism, select one of them to establish a communication connection, and ensure that the communication proceeds smoothly. Anti-collision technology and error correction algorithms ensure the quality of data communications. 5, data security In order to ensure data security, many radio frequency identification systems now employ password function units to prevent malicious reading and writing of memory. Access to the storage area is subject to authentication between the reader and the non-contact IC card. For data integrity 5, data security is called mutual authentication based on the international standard ISO 9798-2 “Three-way mutual authenticationâ€. During the communication, both parties mutually check each other's password. The mutual authentication process starts by sending a "query password" from the reader to the non-contact IC card. The non-contact IC card generates a random number Ra and sends it back to the reader. The reader generates a random number Rb, and uses a common key K and a common cryptographic algorithm ek to calculate an encrypted data block Token1 and sends this data block to the non-contact IC card. Token1=ek(Rb||Ra||Ida||Message 1) The non-contact IC card decodes and receives Token1, and compares the random number Ra' obtained from the plaintext message with the previously transmitted random number Ra. If the two numbers match, the non-contact IC card confirms that the two common passwords are the same. The non-contact IC card additionally generates a random number Ra2 and calculates the encrypted data block Token2. Token2=ek(Ra2||Rb||Ciphertext 2) The reader decodes Token2 and checks whether the originally sent Rb is consistent with the newly received Rb'. If the two random numbers match, the reader also proves that the two common passwords are the same. Thus, both the non-contact IC card and the reader have been verified as belonging to a common system, and further communication between the two parties can be conducted. High Precision Parts,Brass Coil,Coil Brass,Brass Coil Stock TAICANG CITY JINXN COPPER TUBE CO.,LTD , http://www.jinxincopperpipes.com