There are two kinds of RFID systems that exist- passive and active. If you're new to RFID, you might be wondering what the difference is between these types, and which one is best for your application.
Passive RFID
Passive RFID systems use tags with no internal power source and instead are powered by the electromagnetic energy transmitted from an RFID reader. Passive RFID tags are used for applications such as access control, file tracking, race timing, supply chain management, smart labels, and more. The lower price point per tag makes employing passive RFID systems economical for many industries.
Generally speaking, three main parts make up in a passive RFID system – an RFID reader or interrogator, an RFID antenna, and RFID tags. Unlike active RFID tags, passive RFID tags only have two main components – the tag's antenna and the microchip or integrated circuit (IC).
As the name implies, passive tags wait for a signal from an
RFID reader. The reader sends energy to an antenna which converts that energy into an RF wave that is sent into the read zone. Once the tag is read within the read zone, the RFID tag’s internal antenna draws in energy from the RF waves. The energy moves from the tag’s antenna to the IC and powers the chip which generates a signal back to the RF system. This is called backscatter. The backscatter, or change in the electromagnetic or RF wave, is detected by the reader (via the antenna), which interprets the information.
As mentioned above, passive RFID tags have no internal power source, and a standard passive RFID tag consists only of an IC and internal antenna; this basic structure is commonly referred to as an RFID inlay. Countless other types of
passive RFID tags exist on the market, but all tags generally fall into two categories – inlays or hard tags. Hard RFID tags are durable and made of plastic, metal, ceramic and even rubber. They come in all shapes and sizes and are typically designed for a unique function, material, or application.
Active RFID
Active RFID systems use battery-powered RFID tags that continuously broadcast their own signal. Active RFID tags are commonly used as “beacons” to accurately track the real-time location of assets or in high-speed environments such as tolling. Active tags provide a much longer read range than passive tags, but they are also much more expensive.
There are two main frequencies used by active systems – 433 MHz and 2.45 GHz. User preference, tag selection, or environmental considerations usually dictate which frequency to use for most applications. Companies generally favor RFID systems that operate on the 433 MHz because it has a longer wavelength enabling it to work a little better with non-RF friendly materials like metal and water.
Active RFID systems have three essential parts – a reader or interrogator, antenna, and a tag. Active RFID tags possess their own power source – an internal battery that enables them to have extremely long read ranges as well as large memory banks.
Transponders – In a system that uses an active transponder tag, the reader (like passive systems) will send a signal first, and then the active transponder will send a signal back with the relevant information. Transponder tags are very efficient because they conserve battery life when the tag is out of range of the reader. Active RFID transponders are commonly used in secure access control and in toll booth payment systems.
Beacons – In a system that uses an active beacon tag, the tag will not wait to hear the reader’s signal. Instead, true to its name, the tag will ‘beacon’, or send out its specific information every 3 - 5 seconds. Beacon tags are very common in the oil and gas industry, as well as mining and cargo tracking applications. Active tag’s beacons can be read hundreds of meters away, but, in order to conserve battery life, they may be set to a lower transmit power in order to reach around 100 meters read range.
Tasked with weathering harsh environmental conditions such as extreme temperatures and moisture, most active RFID tags are encased in a rugged shell. Because of the size of the enclosed battery, circuitry, and bulk of a durable exterior,
active RFID tags are usually much larger than passive tags. Also, some active tags may have on-board sensors that track environmental parameters. These sensors can track moisture levels, temperature, and other key identifiers that a company can use for their application.
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