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What is Active RFID
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What is Active RFID

Generally, there are two kinds of RFID systems—Passive RFID system and Active RFID system. They have different operating principles and applications. In order to replace barcode system, passive tags should be as cheap as possible. For a simplest Passive RFID system, it should include two main parts. One is passive tag another is reader. A passive tag does not need a battery. Its required energy is from a reader. The basic operating principle is shown in Figure 1.2.1


Figure 1.2.1 Basic principle of Passive RFID

Figure 1.2.1 is a basic passive RFID system. It involves Tags and Readers. A tag that is attached to the object to be identified is the actual data carrier device of an RFID system. Inside a passive tag there must include several main models—rectifier, clock extracting circuits, modulation and demodulation circuits, logic control circuits, coding and decoding circuits, memory, and antenna. All these circuits need power. The energy for these circuits is from Reader. When a reader sends continuous wave to a tag, a rectifier inside tag will directly convert the continuous wave to DC. This DC current is the power source of all circuits in a tag.

Active RFID system is another kind of RFID system and it is more like a small communication system. It includes two main parts—Reader and Tag. The most significant character of Active RFID is that there is a battery inside an active tag. There is a transceiver inside every tag for long distance communications. An important issue in design an active RFID system is a power saving method. Another important issue is the cost of a tag. The performance of an active RFID tag will also be affected by a metallic background when a tag is directly attached to a metallic object.

Compared to a passive RFID system, the active RFID system has its own benefits [3]. First of all, the communication range of active RFID system is larger than passive RFID system. Secondly, the memory size of active RFID system is larger than passive RFID system. Further more the memory size of active RFID system is easily expanded and this is depended on different requirements. Thirdly, tags may be able to talk to other tags. This is very important in some applications. Using Tag-to-Tag communication can efficiently avoid blind area which is generated by blocking of EM wave. Fourthly, various sensors can be combined with tags to monitor the environments around tags. This kind of application is useful for harmful gas monitor or preventing a forest fire. Sometimes battery can drive other functions such as GPS or a display. Thus how to save more power is the biggest issue of an active RFID system. Compared with passive RFID systems, the active tag is larger and more expensive.

 The differences between RFID technology and other identification technologies

With the rapid development of RFIC and the low power microprocessor technology, RFID technology has been becoming one of the most important technologies in the twenty-first century. RFID technology will be widely employed in our everyday live. The technology can be used in retail, warehouse management, tracking items, location, airport luggage management, supply chain, even home security for improving productivity and efficiency.

Among all applications, supply chain is the biggest beneficiary of RFID technology. A supply chain is complex. The core of supply chain is the management process. Usually the process includes three phases—Procurement, Purchasing, and Support [1]. These three phases involve customer business requirements, creation of a purchase order, the shipment of the finished goods, receipt of the finished goods, and so on. Every small goods in this complex supply chain should be tracked at every step of the process. We can image if all these small steps are recorded by paper, how complex they will be. Even we use barcode to identify every small goods, the work load is still very heavy because all goods need to be scanned at least one time by hand and sometimes they need to be scanned several times because of the dust or spot on the surface of them.. Furthermore, from the size of barcode we know that the data density is low. One barcode can not carry a large data quantity. For a typical barcode its data quantity is 1~100 byte. For instance, UPC-A barcode is composed of 12 digits and EAN-13 is composed of 13 digits. This data size is not enough for every small item to have any detail description of their properties. From all these requirements we finally recognize that a new technology must be employed. RFID technology is developed for this kind of application and now it extends to many other regions.

There are many identification technologies. For instance, Optical character recognition, Biometric procedures, Voice identification, Fingerprinting procedures, Smart cards, Memory cards, and Microprocessor cards can all be used for identification

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