In General

Both Active and Passive technologies use radio frequency energy to communicate between a tag and a reader but the method of powering the tags is different. Simply speaking, Active RFID uses an internal power source (battery) within the tag for its RF communication whereas Passive RFID does not have its own power source but relies on RF energy transferred from the reader to the tag to power the tag. Passive tags and labels are smaller allowing them to be used widely, whereas Active tags are larger (due to the presence of battery and onboard sensors) .

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.

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.

 

 

FeaturesActive TagsPassive Tags
Power source Internal power source (typically a battery)No internal power source (powered by the RFID reader)
Read range Considerably longer read rangesShorter read ranges
Cost More expensiveLess expensive
Maintenance 

3-5 year lifespan* (must be disposed of and replaced when the battery dies)

*Unless built with a replaceable battery.

Indefinite lifespan, depending on environmental factors (typically 10+ years)
Signal availability Always on (optional)Responds when powered by the RFID reader
SizeLarger and bulkier than passive tags due to the embedded batterySmaller than active tags
Embeddable Cannot be easily embedded due to sizeCan be easily embedded

 

Detailed explanation

Passive RFID

Passive RFID System generally comprises a RFID reader, RFID antenna, and RFID Tags. The system can operate in the low frequency (LF), high frequency (HF) or ultra-high frequency (UHF) ranges. Unlike active RFID tags, passive RFID tags only have two main components – the tag’s antenna and the microchip or integrated circuit (IC). Passive RFID Tags are available in various shapes and sizes and are easy to attach; sometimes they are embedded into adhesive labels.These tags are disposable and hence are ideal for applications where reusable tags are not needed. DVD kiosks, IT asset tracking, file tracking, laundry management are the typical applications of Passive RFID which do not require a long read range.

Passive RFID tags do not all operate at the same frequency. There are three main frequencies within which passive RFID tags operate. The frequency range, along with other factors, strongly determines the read range, attachment materials, and application options.

125 – 134 KHz – Low Frequency (LF) – An extremely long wavelength with usually a short read range of about 1 – 10 centimeters. This frequency is typically used with animal tracking because it is not affected much by water or metal.

13.56 MHz – High Frequency (HF) & Near-Field Communication (NFC) – A medium wavelength with a typical read range of about 1 centimeter up to 1 meter. This frequency is used with data transmissions, access control applications, DVD kiosks, and passport security – applications that do not require a long read range.

865 – 960 MHz – Ultra High Frequency (UHF) – A short, high-energy wavelength of about a one meter which translates to long read range. Passive UHF tags can be read from an average distance of about 5 – 6 meters, but larger UHF tags can achieve up to 30+ meters of read range in ideal conditions. This frequency is typically used with race timing, IT asset tracking, file tracking, and laundry management as all these applications typically need more than a meter of read range.

As a general rule, higher frequencies will have shorter, higher-energy wavelengths and, in turn, longer read ranges. Moreover, the higher the frequency, generally speaking, the more issues an RFID system will have around non-RFID-friendly materials like water and metal.

 

Advantage of  Passive RFID:

  • Smaller tags
  • Much cheaper tags
  • Thinner/more flexible tags
  • Higher range of tag options
  • Tags can last a lifetime without a battery (depending on the wear and tear)

 

Active RFID

As mentioned earlier Active RFID system uses battery-powered RFID tags to transmit its own signal. So, an active RFID tag consists of a battery, and an active transmitter. Since the active tag has its own power source it does not depend on the reader signal to generate a response. Active RFID Tag is capable of receiving very low-level signals, and then generating high-level signals back to the reader. Moreover, the Active RFID tag is continuously powered. Active tags can also transmit a periodic beacon to a reader (or other tags) in certain situations.

Essentially, two different types of active RFID tags are available – transponders and beacons.

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.

The presence of own power source in Active tag allows it to have extremely long read ranges, with read distances of up to 100 meters or more seeming quite common. The presence of onboard power source also bestows the tag with large memory. Active tags may be either read-only or read/write, thus allowing data modification by the reader.

Since Active tags can be read at much greater distances they are able to collect thousands of tags from a single reader. Additionally, some Active tags can contain external sensors to monitor temperature, humidity, motion, and other conditions. Due their long reading range, Active Tags are ideal for applications which require long range scanning.

There are two main frequencies used by active systems – 433 MHz and 915 MHz. 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.

Typically, active RFID tags are powered by a battery that will last between 3 – 5 years, but when the battery fails, the active tag will need to be replaced. As the active tag market matures, replaceable batteries will be a cost saving option. The system’s functionality depends entirely on the type of tag chosen for the application.

The prices of active RFID tags range anywhere from $20 to $100+ depending on the tag’s ability to withstand harsh conditions and other key functional features of the tag. Given the required investment of an active RFID system, active tags are usually reserved for tracking high worth assets or for items where accurate location tracking is necessary to the success of the system. A few examples of these type of assets are pipes, cargo containers, and machinery.

Advantage of Active RFID Tags:

  • Extremely Long Read Range
  • Increased tag abilities with partnered technologies (GPS, sensors, etc.)
  • Extremely Rugged tag options

 

 

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