Active Vs. Passive RFID For Location Tracking [2018 UPDATE]

Wondering about how similar—or how different—active and passive RFID are? Here’s a quick rundown on the two radio frequency technologies:

Passive RFID uses high-power readers that send out a low-frequency, high-power RF signal to battery-free tags. The antenna in the tag is woken up by the amount of energy flowing to it, which wakes up its circuit. The tag then transmits a coded message back to the reader at a different frequency. Passive RFID technology is often used for inventory tracking and to deter theft.

Active RFID, on the other hand, uses battery-powered tags that advertise their identity to various access points or readers. These access points often then transfer the location of each tagged item to a gateway. Active RFID technology can be used for various forms of asset location management.

As you can tell, active vs. passive RFID serve very different use cases—and in fact, there are very few times when you would have to choose between the two for your tracking system. To make the differences even more clear, we’ve broken out the important characteristics of each and compared them below.

Active Vs. Passive RFID: A Comparison

Use Case & Range	Is your goal to keep track of inventory located in a specific room? If so, passive RFID is probably ideal for you. But if you need to actually monitor the physical location of a tagged object throughout your entire building, active RFID will be your best bet. It comes down to scalability and functionality. Passive readers can only read tags roughly one to five meters away—so scaling a system that would work for actually tracking the location of an item would require a large number of readers. Active RFID systems, on the other hand, scale easily because a reader can detect a tag farther than 100 feet away. This means you could, in some instances, cover 10,000 square feet with only one reader and a few reference points. AirFinder active RFID tags, for example, calculate their location relative to reference points and send this data to nearby readers. The readers then send the location data to the gateway, which is then sent to the AirFinder web application. The application takes the data and provides the user with an estimated location of each tagged asset.
Tag Cost	If the cost of the tag is the main driver in your decision, passive RFID will win every time. Passive tags are typically between 10 and 50 cents each, whereas active tags range between $5 and $15 each.
Battery Life	Passive RFID tags are simple and battery-free—meaning they’ll last virtually forever, which is a big part of their appeal. Active RFID tags, on the other hand, typically last between three to five years, with some lasting up to 10. While passive is the clear winner when it comes to tag longevity, it’s worth noting that active RFID tags are known to have a much better battery life than some other RTLS technologies (like ultra wide-band and WiFi).
Environmental Constraints	Passive tags are easier to completely seal, which makes them more suitable for for more ruggedized environments. Since active tags require batteries, it’s more difficult to ruggedize them. Keep in mind that active tags also cannot always withstand the autoclaving process—so if sterilization is required for your tracking use case, you’ll want to consider all your options.

Could active and passive RFID work in tandem?

Yes! In fact, that’s something AirFinder is examining for the future. We’re currently looking into adding passive functionality into our active tags, for two reasons. First, it can provide time-sensitive chokepoint functionality, so we’ll be able to tell more accurately if a tagged item leaves a particular area. Second, it gives those who require active RFID scalability but could use passive RFID functionality a better option in the market. Stay tuned for updates!