|
|
|
|
|
Computing and technology have moved from dedicated systems and servers to personal everyday items, like watches, tools, appliances and even clothes. The way it happens is that in each of these you can embed a computer, with its own circuitry, a microprocessor and some memory—and in some cases, even the operating system. Embedded computers have the potential to be ubiquitous, yet invisible, which has earned embedded computing an alternative name—pervasive computing. The real impact of an embedded computer is when it interacts with others in a network, giving you seamless connectivity and access to information. RFID is a manifestation of embedded computing. The readers and tags all have embedded computers—with an antenna and a programmed transponder—that communicate with the rest of the network. There is work on to make the embedded computers in RFID have more memory, wider reading ranges, and faster processing. An RFID system consists of three main things—an antenna, a transceiver and a transponder. The reader, which has an antenna in it, sends out electromagnetic waves, which form a magnetic field when they couple with the antenna on the RFID tag. A passive RFID tag draws power from this magnetic field and uses it to power the microchip’s circuits. The chip then modulates the waves that the tag sends back to the reader, and the reader converts the new waves into digital data. Depending on the frequencies they operate in and the level of access they provide, there are several kinds of tags and readers for different needs. The information from them is read either by computers on the network, by PDAs or by special RFID readers. While most RFID devices have an embedded chip in them, chipless RFID is also possible and prevalent. Instead of storing information on a chip, chipless RFID uses electromagnetic material like special fibers, laminates and fine wires to store data. These become passive antennas undetectable to the eye, and particularly suited to security applications. For chipless antenna, the read range is usually no more than a few inches, but there are some that can read as much as ten meters. They also have limited memory. But on the good side, they are usually much more economical than those with a silicon chip. They are also much more flexible in how they can be used—they can be applied in more diverse environments, because they work over a wider temperature range and are less sensitive to interference. They can be implemented in thin packaging and labels and be invisible to the naked eye. If you need to work with non-metallic or non-conductive materials, then the regular chip-based sensors don’t work. For this, capacitive sensors are used. Capacitive switches can detect both conductive and nonconductive objects such as water and other liquids, plastics, wood, glass and a variety of other materials. They are ideal for product detection because of their ability to detect non-conductive targets. Capacitive sensors and tags have low power consumption, very high sensitivity, stability and durability, and are virtually insensitive to temperature variations. With so many standards and products, there is a need for tags and readers to be able to jump among the different communication techniques used by different systems, providing a common interface for users and increased manufacturing volume for suppliers. Such readers are available and are called Agile Readers. In the absence of any formal standards in most cases, these readers give the feel of an open standard by emulating a variety of existing tags. Employing agile readers means you can put in a single infrastructure to read multiple tags, so when more are added in the future, you don’t have to look for proprietary ones. The advantage of agile readers is demonstrated by the fact that the world’s biggest retailer Wal-Mart has asked its suppliers to deploy them. Printed RFID and Ink-Based Technology Apart from chips and fibers, sometimes electromagnetically charged chemicals are also used as the base in RFID sensors. In this form, they can be used in innovative electronic ink and printed on to paper. The most useful application of this is in bank notes, to stop counterfeits. It is also useful for protecting paper documents from unauthorized copying. Apart from being printed on to paper, RFID sensors can also be in the paper, which would be useful for defense installations and financial institutions. If all photocopies and prints are taken on this kind of paper, any non-embedded paper can be stopped from going out, and all embedded paper can be tracked. There are instance when just one reader is installed for several antennas, usually when you don’t want to incur the cost of several readers, but still need to increase coverage. In such cases, multiplexed antenna arrays are used. |