What is RFID?


Radio Frequency Identification (RFID) is a generic term for technologies that use radio waves to automatically identify people or objects. There are several methods of identification, but the most common is to store a unique serial number that identifies a person or object, and perhaps some other additional information. The information is stored on a microchip that is attached to an antenna (the chip and the antenna together are called an RFID transponder or an RFID tag). The antenna enables the chip to transmit the identification information to an RFID reader. The reader converts the radio waves reflected back from the RFID tag into digital information that can then be passed on to computers that can make use of it.


RFID is used for everything from tracking livestock and pets to managing automotive supply chain systems. RFID technology can deliver benefits in many areas, from tracking work in processes to speeding up throughput in a warehouse. As the technology becomes standardised, it will be used more and more to track goods in the supply chain. The aim is to reduce administrative error; labour costs associated with scanning bar codes; internal theft; errors in shipping goods and overall inventory levels.


RFID systems operate at different radio frequencies, which have different characteristics that make them more useful for different applications:


Low-Frequency, 125 kHz (LF) tags use less power and are better able to penetrate non-metallic substances. They are ideal for scanning objects with high water content, such as fruit, but their read range is limited to less than a foot (about 30 cm).


High-Frequency, 13.56 MHz (HF) tags work better on objects made of metal and can work around goods with high water content. They have a maximum read range of about three feet (1 metre).


Ultra High Frequency, 868 MHz (UHF) tags typically offer significantly better range (over 8 m) and can transfer data faster than low and high frequencies. But they use more power and are less likely to pass through materials. Also, because they tend to be more ‘directed’, they require a relatively clear path between the tag and reader. UHF tags might be better for scanning boxes of goods as they pass through a dock-door into a warehouse.




























How does an RFID System Work?


An RFID system consists of a tag made up of a microchip with an antenna, and an interrogator (reader) with an antenna. The reader sends out electromagnetic waves. The tag antenna is tuned to receive these waves. A passive RFID tag draws energy from the field created by the reader and uses it to power the microchip's circuits. The chip then uses backscatter modulation to communicate back with the reader.






















Depending on the particular application, the tag data is subsequently relayed onto higher-level ‘enterprise’ systems. These systems are typically connected to database-driven applications which are used to perform stock, inventory and asset-tracking operations at the client side.


RFID Standards & Radio Regulations


A number of international standards have been adopted for some very specific applications, such as for tracking animals and for smart cards, which require encryption to keep data secure. Many other standards initiatives are under way. The International Organization for Standardization (ISO) is working on standards for tracking goods in the supply chain using high-frequency tags (ISO 18000-3) and ultra-high frequency tags (ISO 18000-6). EPC Global, a joint venture set up to commercialize Electronic Product Code technologies, has its own standards process, which was used to create bar code standards. EPC Global has submitted the second-generation (Gen2) UHF EPC protocols to ISO, and it has been approved as ISO 18000-6C, an international standard.

Different countries have allotted different parts of the radio spectrum for RFID, so no single technology optimally satisfies all the requirements of existing and potential markets. The industry has worked diligently to standardize three main RF bands: low frequency (LF), 125 to 134 kHz; high frequency (HF), 13.56 MHz; and ultrahigh frequency (UHF), 860 to 960 MHz.


Most countries have assigned the 125 or 134 kHz areas of the spectrum for low-frequency systems, and 13.56 MHz is used around the world for high-frequency systems (with a few exceptions), but UHF systems have only been around since the mid-1990s, and countries have not agreed on a single area of the UHF spectrum for RFID.


UHF bandwidth across the European Union is regulated by ETSI, and ranges from 865 to 868 MHz, with interrogators able to transmit at maximum power (2 watts ERP) at four 200 KHs channels between 865.6 MHz - 867.6 MHz.


RFID bandwidth in North America is regulated by the FCC, and ranges from 902 to 928 MHz, with readers able to transmit at maximum power (4 watt EIRP) for most of that bandwidth. Note that European transmission channels are restricted to a maximum of 200 kHz in bandwidth, versus 500 kHz in North America. China has approved bandwidth in the 840.25 to 844.75 MHz and 920.25 to 924.75 MHz ranges for UHF tags and interrogators used in that country.


Strength levels at fixed distances from the transmitter (RFID reader) loop antenna. ETSI defined signal strength limitations are depicted below.

Schematic diagram of a typical UHF automotive RFID portal

Reader to Tag Communication

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