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RFID and the Differences in Passive, Semi-Passive and Active Tags

RFID | 24 April 2019

Posted by Josh Miller

RFID and the Difference in Passive, Semi-Passive, and Active Tags

While there are several classifications of RFID, one of the most common ways it is categorised is whether the tag is passive, semi-passive, or active. In this discussion we will dissect what makes these tags different from one another, and the answer lies in their functions, features and ideal applications.

Passive

Passive tags are typically made up of two parts, an integrated circuit and an antenna. There are no additional moving parts or batteries, just the bare necessities. Without a battery, these tags receive power as they are being read during a process called inductive coupling.

Find More Information about Coupling in our Blog Post about the Relationship  Between a Tag and a Reader

Since these tags only run when needed, they tend to have a long and stable lifespan and the lack of moving parts reduces failure points, these benefits don’t come without tradeoffs though. Some of the downsides to passive RFID include less data storage, inability to add features and the need for data middleware or software to do the heavy lifting.

To some the lack of additional features may be a deal breaker, but to others the simplicity of passive RFID is what makes it so appealing. The long lifespan and reliability of passive RFID make it a great choice for anything being stored for an extended period of time. Additionally, passive RFID tends to be a more cost effective option, so in applications where the tagged item doesn’t need to be tracked for long it’s a good match.

Semi-passive

Semi-passive tags contain an integrated circuit, an antenna and a battery, but aren’t limited to those three pieces.

The inclusion of a battery in semi-passive tags allows additional features such as sensors, real time tracking and sound notifications to be applied to the tags. The only additional feature you can’t find on a semi-passive tag is an onboard transmitter since it’s the main attribute that differentiates semi-passive tags from active tags. Without an onboard transmitter, the read range of these tags is limited, and with the inclusion of a battery so is their lifespan.

What really differentiates semi-passive RFID from both active and passive RFID is the inclusion of a battery and its lack of an onboard transmitter, which give these tags the ability to support additional features without increasing read range. Because of these features semi-passive RFID is best suited for applications where additional features such as environment monitoring are necessary and the tagged items remain within range of the reader.

Active

Active RFIDActive tags are made up of an integrated circuit, antenna, battery and onboard transmitter. The onboard transmitter serves the purpose of sending energy directly to the reader rather than reflecting back the energy the reader transmitted to the tag, increasing the read range.

Along with the increased read range, active tags have the ability to adopt numerous additional features including integrated sensors, increased memory and more logic. Since active tags have more parts than any other tag, and are optimised to host extra features, they tend to take up more space than any of the other tags. The cost of active RFID tags also tends to be higher due to the increased materials and special features. Additionally, these tags tend to have a shorter lifespan as their power is used up faster by the transmitter and any extra moving parts.

Businesses working with valuable goods that need constant real time tracking and/or environmental control are the best match for active RFID. In situations where products are sensitive or security is a concern, active RFID is a worthy investment to ensure your products are safe and sound.

Now that you know the difference between passive, semi-passive and active RFID, you’re one step closer to finding your ideal RFID strategy. Choosing the right activity level for your RFID plan is only one of several factors you’ll need to consider prior to implementation, and we are here to help you along your research journey. For more information continue reading our blogs or contact us.

Continue Your Research By Learning The Difference Between Low, High and  Ultra-high Frequencies >

Josh Miller

Josh Miller is Computype’s Director of Healthcare Solutions. With many years in both project management and engineering, he is able to provide expertise and valuable insight throughout our company and to our customers. Josh oversees the healthcare group and drives innovation to ensure we’re offering the best solutions.