Radio Frequency Identification Done by: Haitham Habli.
Table of contents Definition of RFID. Do they need license? RFID vs other identification systems. Classification of RFID systems. Emerge of passive RFID systems. Operation of data transfer in low-frequency simplified passive RFID tags. What materials RFID tags can be encased in? Backscatter RFID system. RFID Tag Integrated Circuit. Applications of RFID. Summary.
what is RFID? Radio frequency Identification is amony the most technically advanced methods of collecting data automatically. RFID system generally consists of three basic components: a transponder, a reader and host data processing system. The transponder is the data-carrying device that is attached to the object that is to be identified. The reader is used to communicate with the transponder s in order to read or write the data inside the transponder s memory. The RFID system is useless without the ability to share the information of the transponders identified by the reader. Therefore, the host data processing system has connection to the closed or worldwide network.
Do they need license? RFID systems operate in the unlicensed RF bands known as ISM (Industrial, scientific and Medical). It is important to note that while ISM devices do not require a license, they are still subject to signal emission limits that vary by country.
RFID vs other identification systems Automatic identification systems include barcode systems, optical character recognition, smart cards and radio frequency identification. RFID is the most sophisticated systems among them. At the moment, using barcodes is very widespread application of carrying identification data with the item. Compared to barcodes, RFID systems don t need the line of sight contact with the reader. RFID systems is also more stable against the vulnerable enviroment factors like dirt and wearing that barcodes and optical character recognition labels face. Biometric body measurements as an identifcation method are only available for living beings. In smart cards the data stored in the memory can be protected but they need a galvanic contact in order to be read.
Few advantages of RFID over barcode Multiple tag identification is possible. It does not require the transponder to be in line-of-sight. RFID can handle environments like moisture, dirt frost etc. We can combine the RFID functionality with Electronic Article Surveillance (EAS).
Classification of RFID systems. Various demands on RFID systems can be set due to different applications. Therefore, different types of RFID systems exist. The RFID systems can be classified into different groups by read range, operating frequency, coupling method and the amount of data and energy supply of the transponder. According to their operating frequency, RFID systems can be divided into near and afr field systems.125 khz and 13,56 MHz systems are near field systems whereas 868 MHz, 915 MHz and 2,4 GHz are far field systems. Near field systems depends on the areas of the antenna coils and their mutual positions. In Far field systems an electric field is used in the coupling and the antennas used are usually dipole, folded dipole (omnidirectional antennas) and microstrip antennas (directional antennas).
Classification of RFID systems. The transponders can either be passive or active. Active transponder have a power source of their own. It has the adavantage of longer reading distance as no power has to be transmitted wirelessly. They can perform data collection tasks even when no reader is present. Passive transponders are powered by the energy radiated by the reader. They are smaller, have lower cost, and require no periodic maintenance. The source of energy to power the passive tags is the magnetic or electromagnetic field that the reader omitts. In case of the electromagnatic coupling the reader uses an antenna to radiate an alternating electromagnetic field at a constant frequency. The antenna of the transponder receives the signal. The rectifier on the IC connected to the antenna terminals converts the recieved signal to the voltage that is used to power the electronics in the transponder.
Classification of RFID systems. The communication procedure in RFID systems can be full duplex (FDX), half duplex (HDX) or sequential. In FDX and HDX procedure communication from transponder is possible when signal from the reader unit is on. In sequential the communication is handled in turns. It's disadvantage is that the wireless power transmitted to the transponder is not continuous and is interrupted when the transponder is responding.
Emerge of Passive RFID systems Passive tags, on the other hand, are very inexpensive; they can cost as little as 20 cents apiece, and new technologies are constantly making them cheaper to integrate into common materials and products. Because passive tags are inexpensive, they will likely be the basis of most of the growth in RFID implementations, so I will examine the technology behind passive tags in detail. In addition to their low cost, passive tags can also be quite small. Current antenna technology limits the smallest useful passive tag to about the size of a quarter. The larger the tag, the larger the read range.
Emerge of Passive UHF RFID systems Passive UHF RFID systems have many features that speak for using them in supply chain managment and product life cycle management. The most important features of them when SCM and PLM are considered are non-line of sight reading and writing of tags, multiple object identification and the ability to read moving objects, relatively long, over 1 m read ranges, possibilties to develop low-cost tags and readers for highvolume applications and the ability to provide a unique identifier for each object using EPC code. Supply chain managment is the mangemnt and control of all materials and information in the logistics process from acquisition of raw materials to delivery to the end user.
Simplified view of data transfer in low-frequency passive RFID tags (the tag is enlarged for clarity).
Operation of data transfer in low-frequency simplified passive RFID tags A passive-tag reader can constantly broadcast its signal or broadcast it on demand. When a tag comes within the reader s range, it receives an electromagnetic signal from the reader through the tag s antenna. The tag then stores the energy from the signal in an on-board capacitor, a process called inductive coupling. When the capacitor has built up enough charge, it can power the RFID tag s circuitry, which transmits a modulated signal to the reader. That return signal contains the information stored in the tag. The communication between the reader and passive tag uses one of two methods to modulate the ID signal. Low-frequency (less than 100 MHz) tags pass information by releasing energy from the capacitor to the tag coils in varying strengths over time, which affects the radio frequency emitted by the tag.the reader detects these varying waves and can use these variances to demodulate the code. Figure shows this load modulation.
In higher-frequency (greater than 100 MHz) tags In higher-frequency (greater than 100 MHz) tags, the tag transmits the signal using backscatter, in which the tag s circuit changes the resistance of the tag s antenna. This change in resistance causes a transmission of RF waves, which the reader can pick up and demodulate. Passive tags typically operate at frequencies of 128 KHz, 13.6 MHz, 915 MHz, or 2.45 GHz, and have read ranges of a few inches to 30 feet. Frequency choice depends on the system s environment, what material the signal must travel through, and the system s required read range
What materials RFID tags can be encased in? RFID tags can be encased in many materials. Plastics are a very common material for RFID, forming identification cards for building access, credit cards or bus fares. Tags can also go on the back of labels printed on standard ink jet printers, for placement on inventory.
Backscatter RFID system.
Backscatter RFID system In the return link from the transponder to the reader, the proportion of incoming RF signal is backscattered from the transponder antenna back to the reader antenna. The processing circuit of the transponder changes the RF impedance of the transponder antenna and controls the amount of this scattered field. In this case the modulation of the scattered field contains the identification information. The transponder is identified when the backscattered field is received and decoded by the reader unit.
Backscatter RFID Transponder.
What happen? The modulated signal from the base station is received by the tag transponder. Voltage induced at the input terminals of the transponder due to the RF field from the base station. This voltage will be detected by the RF front end circuit of the chip and this DC voltage will be used to charge a high capacitor and provide the necessary bias for the processing circuitry. The response of the transponder is determined by the voltage induced on the transponder that exceeds a threshold voltage, which depends on the properties of the detection circuit attached to the transponder antenna.
What happen? The processing circuit on the chip responds to the base station commands according to the protocol and provides a change in the in the RF impedance and hence provides a detectable back scattered signal to the base station. Depending on the sensitivity of the receiver and the minimum transponder threshold voltage we can establish a read /write range from the base station. Data can be either read from any memory location of the chip or can be written to any specified location.
RFID Tag Integrated Circuit Block Diagram
The basic components in the chip are EEPROM RF front end Analog section Digital Section Storage device / battery
Typical chip specifications are: Ultra low power 5-15 micro-watts during read operation and 80-120 micro-watts during write operation. Forward and return links use different types of modulation schemes. EEPROM total 128 bytes. System reserved memory 8 bytes. Tag identifier (ID) 8 bytes. User memory 112 bytes. Operating temperature -40 to 175'C.
Applications of RFID. RFID can be widely used in the applications like retail, transportation, access control, asset management, supply chain, electronic anti theft. Few promising applications are source tagging, self check out, video rental, parking, auto registration, non-stop toll collection, access control, badge readers, subway entry, theme parks, warehouse inventory, package handling, parcels, mail, pallets, etc.
Find on wikipedia more on appliactions Current uses: Passports Transport payments Product tracking Automotive Animal identification RFID in inventory systems Human implants RFID in libraries and others applications. Potential uses: Replacing barcodes Telemetry Patient identification
summary They dont need license. Founding many application in logistics. RFID is certainly a usefull alternative identification tool in applications where large data storages are essential. getting cheaper. However the important point in the design is the matching between the front end and the input of the tag antenna terminals. A careful matching network design is the key for obtaining the best performance.
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