Passive RFID Tag (or Passive Tag)
A passive tag is an RFID tag that does not contain a battery or have a power source, but simply reflect back or backscatter the energy coming from the reader antenna. They can therefore only operate in the presence of a reader. The communication range is limited by the need for the reader to generate very strong signals to power the tag, which therefore limits the reader-to-tag range. Passive tags are less expensive offer a virtually unlimited operational lifetime Passive tags are comprised of three elements: an integrated circuit or chip, an antenna, and a substrate. The RFID chip stores data and performs specific tasks. Depending on its design, the chip may be read-only (RO), write-once, read-many (WORM), or read-write (RW). Attached to the chip is the antenna, whose purpose is to absorb radio-frequency (RF) waves from the reader's signal and to send and receive data. Passive RFID tag performance is strongly dependent on the antenna's size: the larger the antenna, the more energy it can collect and then send back out. Larger antennas, therefore, have higher read. The third component of a passive RFID tag is called a substrate, which is commonly a Mylar or plastic film. Both the antenna and the chip are attached to the substrate, which may be thought of as the "glue" that holds all of the tag's pieces together.
A semi-passive tags operate similarly to passive RFID tags. However, they contain a battery that enables longer reading distance and also enables the tag to operate independently of the reader. A Semi-Passive Tag is a medium cost tag containing a microchip, antenna and battery. Semi-passive tags communicates with an interrogator via backscatter or inductive coupling, like passive tags, but have faster response times and greater memory capacity due to the battery. Semi-passive Tag Systems require the tag to use battery power for the digital logic on the chip, but still use harvested power for communication. Semi Passive tags have greater read ranges than purely passive tags, but they also have shorter lives (due to their reliance on battery power) and are significantly more expensive.
A smart label contains the RFID tag as well as printed bar codes and alphanumeric characters. The printed material can provide redundant UPC and EPC data that can be picked up by a bar code scanner or read by a warehouse employee if the RFID tag cannot be read. RFID smart labels are printed and encoded at the same time in an RFID printer. The RFID portion of the smart label is called an "inlay" and is adhered to the back of the paper label. Smart labels are applied directly to packages or to pallets or other containments.