What is the best type of RFID interrogator for tracking the rough location of an active RFID tag within a building?
There are various types of active tags that employ different air-interface protocols—the language, if you will, that tags and readers use to communicate—and different frequencies, including 433 MHz, 915 MHz and 2.45 GHz. So it's not a question of finding an interrogator that can locate a tag—it's a question of finding a system that will do what you need it to do in order to drive business benefits.
Among the aspects to consider is how precisely you need to locate a tag. Is a few meters sufficient, or do you need to locate it within a few centimeters? Ultra-wideband (UWB) systems can pinpoint a tag with more precision than other active systems. Another question is whether tagged items will move through a specified zone. If you need to know that a tagged item has, say, left one area and entered another, then a system based on the ISO 18000-7 standard might do the trick.
A third parameter to consider is the nature of the environment. A few very large rooms will likely require a different system than an environment in which you have many smaller rooms (such as in a hospital). It's not RFID, but Sonitor offers a system that utilizes ultrasound, which is very effective for determining in which room a tagged item is located, because sound waves don't pass through walls, as does RF energy.
There might be other factors that you will need to consider as well, such as the size of the item being tagged. A good systems integrator can help you work through these issues and find the best system for your particular needs.
—Mark Roberti, Editor, RFID Journal
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