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21-12-2009, 10:09 AM
Almost every product in the market has a barcode printed on it. Barcodes are machine-readable parallel bars that store binary information, revealing information about the product. Thus, it acts as the product fingerprint. As we go to the supermarket to buy things, the checkout person runs our selection over the scanner to scan the barcode, thereâ„¢s an audible beep, and we are told how much money we owe.
But the days of barcode are numbered. The reason is that a technology called radiofrequency identification (RFID) is catching on.RFID tags are being used by corporations to track people and products in just about every industry. They transform everyday objects like cargo containers, car keys, and even clothes on the rack at a shopping mall into mini nodes on a network. Databases then record the location and status of these network nodes to determine product movements.This technology can completely replace barcodes.The automotive industry makes use of small RFID tags that offer a high level of security at low cost.
A tag is any device or label that identifies the host to which it is attached. It typically does not hinder the operation of the host or adversely affect its appearance.
The word transponder is derived from the words transmitter and responder. The tag responds to a transmitted or communicated request for the data it carries.
The transponder memory may comprise of read-only (ROM), random access (RAM), and non-volatile programmable memory for data storage depending on the type and sophistication of the device. The ROM-based memory is used to accommodate security data and the transponder operating system instructions which in conjunction with the processor or processing logic deals with the internal Ëœhouse-keepingâ„¢ functions like response delay timing, data flow control and supply switching. The RAM-based memory is used for temporary data storage during transponder interrogation and response. The non-volatile programmable memory may be of several types of which the electrically erasable programmable read-only memory (EEPROM) is the most common. It is used to store the transponder data and needs to be non-volatile to ensure that the data is retained when the device is in its quiescent or power-saving Ëœsleepâ„¢ state.
Data buffers are further components of memory used to temporarily hold the incoming data following demodulation and outgoing data for modulation and interface with the transponder antenna. The interface circuitry provides the facility to direct and accommodate the interrogation field energy for powering purposes in passive transponders and triggering of the transponder response. The transponder antenna senses the interrogating field and serves as the means for transmitting the transponder response for interrogation.
CLASSIFICATION OF TAGS
On the basis of the presence of battery, tags can be classified into active or passive tags.
Active tags are powered by an internal battery and are generally read/write devices. They contain a cell having a high power to weight ratio and are capable of operating over a temperature range of -50 to +70 degree Celsius. Active tags have a finite life time. A suitable cell coupled to suitable low power circuitry can ensure functionality of ten or more years depending on operating temperatures, read/write cycles and usage. They have greater size and increased cost compared to passive tags.
Passive tags operate without an internal battery source, deriving the power to operate from the field generated by the reader. They are hence lighter than active tags and have greater life time. They have shorter read ranges compared to active tags. They are also constrained in their ability to store data and perform well in electromagnetically noisy environments
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