Rfid Implementation

RFID--What is it?

Overview

RFID (Radio Frequency Identification) is a means of storing and retrieving data through

electromagnetic transmission to an RF compatible integrated circuit, and is now being seen as a

radical means of enhancing data handling processes.

A range of devices and associated systems are available to satisfy an even broader range of

applications. Despite this diversity, the principles upon which they are based are quite straight

forward, even though the technology and technicalities concerning the way in which they operate

can be quite sophisticated.

Physics and Electronic Foundations

System Components

RFID systems have several basic components or technical characteristics that define them.

These are:

* A reader, including an antenna

The device that is used to read and/or write data to RFID tags.

* A tag

A device that transmits to a reader the data.

* The communication between them

RFID uses a defined radio frequency and protocol to transmit and receive data from tags.

Types of RFID Tags

RFID tags can be segregated into two major classifications by their power source:

* Active tags

Active tags contain both a radio transceiver and battery to power the transceiver.

Because there is an onboard radio on the tag, active tags have substantially more range

(~300 feet) than passive or "active/passive tags." Active tags are also considerably more

expensive than passive tags and, as with any battery-powered product, the batteries

must be replaced periodically.

* Passive tags

Passive tags can be either battery or non-battery operated, as determined by the

intended application. Passive tags reflect the RF signal transmitted to them from a reader

or transceiver and add information by modulating the reflected signal. A passive tag does

not use a battery to boost the energy of the reflected signal. A passive tag may use a

battery to maintain memory in the tag or power the electronics that enable the tag to

modulate the reflected signal.

o Battery-less ("pure passive" or "beam powered")

Pure passive tags do not contain an internal power source such as a battery, and

are thus easier, and less expensive to manufacture. These purely passive or

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"reflective" tags rely upon the electromagnetic energy radiated by an interrogator

to power the RF integrated circuit that makes up the tag itself.

o With a battery ("active/passive")

There is a version of a passive tag that does contain a battery. This type of

passive tag has some of the enhanced, and speed attributes of a true active tag,

but still communicates in the same method, as do other passive tags. These

active / passive tags that do contain an internal power source, usually are much

more complex integrated circuits with multiple components. Consequently, they

are more expensive to make and purchase.

RF tags can also be distinguished by their memory type:

* Read / write

Read / write memory just as the name implies, can be read as well as written into. Its

data can be dynamically altered.

* Read only (typically "chipless")

Read only type of tag memory is factory programmed and cannot be altered after the

manufacturing process. Its data is static.

Read only memory is the less expensive of the two. As RFID markets and applications grow, this

price difference will become less for overall system cost justification.

Types of Communication

antenna

Inductive Coupling Propigation Coupling

tag

antenna

signal signal

tag

Tags and a reader communicate by wireless signal in a process known as coupling.

Two methods of wireless signal distinguish and categorise RFID systems:

* Close proximity electromagnetic, or inductive coupling

* Propagating electromagnetic waves.

Coupling is via antenna structures forming an integral feature in both tags and readers.

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Transmitted data is influenced by the channels through which it must pass, including the air

interface. Structuring the bit stream to ensure error-free, asynchronous data transfer through this

channel is often referred to as channel encoding. Although transparent to the user of an RFID

system this coding scheme is important to engineers