Transcript Chip tag
Chip tag A radio-frequency identification system uses tags readers send a signal to the tag and read its response RFID tags can be either passive active or battery-assisted passive A passive tag is cheaper and smaller because it has no battery The RFID tag receives the message and then responds with its identification and other information. Passive radio frequency identification (RFID) is an automatic wireless data collection technology where RFID reader transmits a modulated RF signal to the RFID tag which consists of an antenna and an integrated circuit chip The chip receives power from the antenna and responds by varying its input impedance and thus modulating the backscattered signal with data. In order to achieve optimum operating condition the antenna impedance should be matched correctly to the chip impedance that is known to change with the received power on the chip as well as with frequency • When both chip impedance and antenna impedance arecomplex, calculatingan accurate power reflection coefficient for tag antenna design is challenging process chip supplied constant values of chip impedances for the three center frequencies that correspond to the primary regional frequencies of operation: Europe (866.5 MHz), North America (915 MHz), and Asia (953 MHz) RFID Tags consist of an antenna and a microchip and the tags get all the energy for functioning from the electromagnetic radiation emitted by the reader through a rectifier, a voltage multiplier and a voltage modulator inside the microchip The tag sends the information backto the reader by switching between two states: One is matched to the antenna and another one is strongly mismatched RFID TAG ANTENNA IMPEDANCE MATCHING The goal of tag antenna designer is to design an antenna that could increase the maximum detection range of the RFID system there are not many antenna parameters that one could use to improve the performance of the tag antenna the omni-directional property of the antenna. As a result, design of a good tag antenna comes down to the enhancement of the reflection coefficient the antenna input impedance should be equal to the complex conjugate of the chip impedance. , the impedance of the microchip is not a constant value and it is a function of both frequency and the received power by the chip The antenna should be conjugate matched to the minimum operational power chip impedance to maximize the tag read range The maximum read range is an important parameter for RFID tag designs. Based on the backscattering theory The maximum read range can be computed from the tag antenna impedance obtained from commercial EM software such as HFSS Radio Frequency Identification (RFID) Tag is a small piece of material, composed of components • a small antenna • a wireless “transducer which may also be linked to a single silicon microchip unit containing memory storage Passive Radio Frequency Identification (RFID) Tag has no power source no on-tag transmitter built onto it which gives a range of less than 10-metres and makes it sensitive to regulatory and environmental constraints Passive tags are generally the lowest in cost suitable for use in large inventories of books and other library media With passive tags, the RFID reader transmits an energy field that activates the tag and powers its chip, enabling it to transmit or store data Active Radio Frequency Identification (RFID) Tag has both an on-tag power source and an active transmitter Active tags are connected to their own battery. They can be read at much higher ranges, up to several kilometres away. However, they are larger and more expensive thanpassive tags Active tags may be programmed to transmit signals, so that data may be captured by multiple readers and distributed throughout a facility Read-Only Chip refers to a chip that can be implanted within an RFID tag that has an identification code recorded at the time of manufacture or when allocated to an object. Read-only tags are therefore much cheaper and are typically used in passive tags Readers have antennas that are used to emit radio waves . The RF energy from the reader antenna is “harvested” by the tag antenna and used to power the tag microchip to reflect back its signal back to the reader The structure of the tag antenna should •low cost •small in size •good impedance matching •and insensitive to the attached objects to keep performance consistent passive RFID system operates in the following way RFID reader transmits a modulated RF signal to the RFID tag consisting of an antenna and an integrated circuit chip. The chip receives power from the antenna and responds by varying its input impedance and thus modulating the backscattered signal One of the tag antenna’s essential functions is to harvest energy from a reader to powerthe tag chip nothing happens until you get power to the tag! And that begins with the right tag chip RFID can store a large amount of information, and physically locate the objects by tags Read-Write Chip refers to a chip, implanted within an RFID tag that can have its memory changed, or written to, many times. Because they enable their ID codes to be changed, readwrite chips offer greater functions but at a greater cost RFID tags using this technology can be read regardless of the material they are on What is the difference between Passive and Active RFID solutions ? passive RFID tags work on the basis that they absorb the power from the reader and use this to empower the microchip and re-emit a signal. Active tags contain abattery, which powers the chip and transmits to the interrogator. As a consequence passive technology tends to be significantly lower cost but restrITed to modest read distances, whereas active solutions are capable of reading over hundreds of meters Dead Tag: An RFID tag that cannot be read by a reader Antenna the conductive element to send and receive tag data. Passive lowfrequency tags (135 kHz) The three main points of design RFID tag antenna is • the size of the tag antenna, • impedance matching between tag antenna and chip, •the environmental factor of the tag antenna performance tag antenna and chip need impedance matching design, in order to effectively improve the energy extracted from the electromagnetic field and increase the operating range (or reading distance) The RFID tag part can also be subdivided into two parts, antenna and tag chip. Each tag contains a unique identification code to identify the attached objects When the tag receives the RF signal from the reader, the tag will "wake up", and according to instructions of the reader to complete the corresponding action, and then send stored target information back to the reader. The storage unit of the tag can be repeatedlyread and written more than 10,000 times Communication through coupling There are two common types capacitive (electrostatic) coupling and inductive (magnetic) coupling.