RFID Journal Staff asked 10 years ago Please explain how this is accomplished.
—Name withheld
———
I'm afraid I do not understand your question. But I'll attempt to offer an answer, based on what I think you are asking.
Multi-port RFID readers can support two, four or eight antennas. A reader uses a multiplexer to turn on and off individual readers in rapid succession, in order to cover, for example, an entire dock door. One reader could actually be used to cover two dock doors. You could place the interrogator in the middle of the two doors, pointing two or four antennas toward one door and the remaining antennas toward the other. You would thus be able to tell through which door a tagged item entered, since the reader would record which antenna interrogated that tag.
Individual RFID reader manufacturers have different ways of identifying antennas, but essentially, they all work the same way. Let's say you have a four-port reader and two doors. You could assign each antenna a number: 1, 2, 3 or 4. Antennas 2 and 4 could be pointed at dock door 1, while antennas 1 and 3 would be pointed at dock door 2. When a tag was read by antenna 3, that information would be recorded, along with the reader and tag ID numbers. So typically, a business could identify, in software, that any tags read by antenna 3 entered dock door 2, and that information could then be stored in the company's inventory-management system.
This type of system is sometimes used to determine the direction in which a tagged item is moving. If antennas were set up on both sides of a doorway, then having a tag read by antenna 1 and then by antenna 4 might indicate that an object was moving into the room, while a tag read first by antenna 4 and then by antenna 1 would signify that the tagged item was leaving the room.
If I have misunderstood your question, please re-submit it with additional details.
—Mark Roberti, Founder and Editor, RFID Journal
Previous Post What Should I Consider When Purchasing a Handheld RFID Reader? »