RFID (Radio Frequency Identification)

RFID (Radio Frequency Identification)

Radio-frequency identification (RFID) is the wireless non-contact use of radio-frequency electromagnetic fields to transfer data, for the purposes of automatically identifying and tracking tags attached to objects. The tags contain electronically stored information. Some tags are powered by and read at short ranges (a few meters) via magnetic fields (electromagnetic induction). Others use a local power source such as a battery, or else have no battery but collect energy from the interrogating EM field, and then act as a passive transponder to emit microwaves or UHF radio waves (i.e., electromagnetic radiation at high frequencies). Battery powered tags may operate at hundreds of meters. Unlike a bar code, the tag does not necessarily need to be within line of sight of the reader, and may be embedded in the tracked object.

History and key developments

            RFID has been around since II World War but was viewed as too limited and expensive in functionality for most of commercial use. With advancement in technology, cost of system components has reduced and capabilities have increased, making RFID more popular.

            Léon Theremin invented a surveillance tool for Soviet Union in the year 1945. This tool retransmitted the incident radio waves along with audio information. Sound waves vibrated diaphragm that altered the shape of resonator, modulating reflected sound frequencies. This tool was not identification tag but a secret listening device. But it is still considered as predecessor of the RFID technology due to it being energized, passive and stimulated by outside electromagnetic waves. Similar technology as IFF transponder was invented in UK in the year 1915 and was regularly used by allies in the II World War for identifying aircrafts as foes or friends. The transponders are used for by powered aircrafts till date.

             Invented in 1973, device by Mario Cardullo is known to be a true ancestor of the modern RFID. Initially the device was passive and was powered by interrogating signals and had transponder 16 bit memory for application as toll device. The basic patent by Cardullo covers application of RF, light and sounds as the transmission media.

            Early exhibition of the reflected power RFID tags, semi passive and passive was presented by Robert Freyman, Steven Depp and Alfred Koelle. This portable system used around 12 bit tags and worked at 915 MHz. And the first patent associated with abbreviation of RFID was approved to Mr. Charles Walton in the year 1983.

Purpose of Radio frequency Identification and Detection system is to facilitate data transmission through the portable device known as tag that is read with the help of RFID reader; and process it as per the needs of an application. Information transmitted with the help of tag offers location or identification along with other specifics of product tagged – purchase date, color, and price. Typical RFID tag includes microchip with radio antenna, mounted on substrate

 The RFID tags are configured to respond and receive signals from an RFID transceiver. This allows tags to be read from a distance, unlike other forms of authentication technology. The RFID system has gained wide acceptance in businesses, and is gradually replacing the barcode system.

How RFID Works

 Basic RFID consists of an antenna, transceiver and transponder. To understand the working of a typical RFID system, check the following animation.

 Antenna emits the radio signals to activate tag and to read as well as write information to it. Reader emits the radio waves, ranging from one to 100 inches, on the basis of used radio frequency and power output. While passing through electronic magnetic zone, RFID tag detects activation signals of reader

 Powered by its internal battery or by the reader signals, the tag sends radio waves back to the reader. Reader receives these waves and identifies the frequency to generate a unique ID. Reader then decodes data encoded in integrated circuit of tags and transmits it to the computers for use.

Types of RFID

 Active and passive RFID are different technologies but are usually evaluated together. Even though both of them use the radio frequency for communication between tag and reader, means of providing power to tags is different. Active RFID makes use of battery within tag for providing continuous power to tag and radio frequency power circuitry. Passive RFID on the other hand, relies on energy of radio frequency transferred from reader to tag for powering it.

 Passive RFID needs strong signals from reader but signal strength bounced from tag is at low levels. Active RFID receives low level signals by tag but it can create higher level signals to readers. This type of RFID is constantly powered, whether in or out of the reader’s field. Active tags consist of external sensors for checking humidity, temperature, motion as well as other conditions.

 What is an RFID reader?

                                 

An RFID reader’s function is to interrogate RFID tags. The means of interrogation is wireless and because the distance is relatively short; line of sight between the reader and tags is not necessary. A reader contains an RF module, which acts as both a transmitter and receiver of radio frequency signals. The transmitter consists of an oscillator to create the carrier frequency; a modulator to impinge data commands upon this carrier signal and an amplifier to boost the signal enough to awaken the tag. The receiver has a demodulator to extract the returned data and also contains an amplifier to strengthen the signal for processing. A microprocessor forms the control unit, which employs an operating system and memory to filter and store the data. The data is now ready to be sent to the network.

                         

RFID Reader Module, are also called as interrogators. They convert radio waves returned from the RFID tag into a form that can be passed on to Controllers, which can make use of it. RFID tags and readers have to be tuned to the same frequency in order to communicate.

               
               An RFID system consists of two separate components: a tag and a reader. Tags are analogous to barcode labels, and come in different shapes and sizes. The tag contains an antenna connected to a small microchip containing up to two kilobytes of data. The reader, or scanner, functions similarly to a barcode scanner; however, while a barcode scanner uses a laser beam to scan the barcode, an RFID scanner uses electromagnetic waves. To transmit these waves, the scanner uses an antenna that transmits a signal, communicating with the tags antenna. The tags antenna receives data from the scanner and transmits its particular chip information to the scanner.
          The data on the chip is usually stored in one of two types of memory. The most common is Read-Only Memory (ROM); as its name suggests, read-only memory cannot be altered once programmed onto the chip during the manufacturing process. The second type of memory is   Read/Write Memory; though it is also programmed during the manufacturing process, it can later be altered by certain devices.

         The RFID tag consists of a powered or nonpowered microchip and an antenna. The three different types of tags are described below.

       Passive tags are the simplest, smallest and cheapest version of an RFID tag as they do not contain a built-in power source and consequently cannot initiate communication with a reader. As the available power from the reader field diminishes rapidly with distance, passive tags have practical read ranges that vary from about 10 mm up to about 5 metres.

       Semi-passive tags have built-in batteries and do not require energy from the reader field to power the microchip. This allows them to function with much lower signal power levels and act over greater distances.

RFID frequencies

            Just like you can tune a radio in various frequencies for listening to different channels, RFID readers and tags need to be tuned in to a same frequency for communication. RFID system uses various frequencies but most common and popularly used frequency is low, high and ultra high frequency. Low frequency is around 125 KHz, high is around 13.56 MHz and ultra high varies between 860-960 MHz. Some applications also make use of microwave frequency of 2.45 GHz. It is imperative to choose right frequency for an application as radio waves work different at various frequencies.

RFID Applications

 The role of RFID is not just confined to Aircraft identification anymore; it is also lending a hand in various commercial uses. Asset tracking is one of the most popular uses of RFID. Companies are using RFID tags on the products that might get stolen or misplaced. Almost each type of Radio frequency Identification and Detection system can be used for the purpose of asset management.

 Manufacturing plants have also been using RFID from a long time now. These systems are used for tracking parts and working in process for reduction of defects, managing production of various versions and increasing output. The technology has also been useful in the closed looped supply chains for years. More and more companies are turning to this technology for tracking shipments among the supply chain allies. Not just manufacturers but retailers also are using this RFID technology for proper placement of their products and improvements in the supply chain.

 RFID also plays an important role in the access and security control. The newly introduced 13.56 MHz RFID systems provide long range readings to the users. The best part is that RFID is convenient to handle and requires low maintenance at the same time.