RFID antennas are useful for keep tracking of inventory and shipments.
Radio frequency identification (RFID) is a technology that uses electromagnetic waves to communicate between a terminal and an electronic tag that is used for tracking and identification purposes. These devices are used by companies that need to keep track of their inventory or need to know where their shipments are in real time. There are three different types of RFID antennas. Each one has different characteristics, advantages and disadvantages. These antennas are used to receive the transmission from RFID tags.
Circular Polarization
The main advantage of the circular polarization antenna is the minimization of fading and signal loss because of its shape. In circular polarization, the electromagnetic waves propagate in two planes completing a 360-degree revolution. The plane of the polarization rotates and makes a corkscrew pattern. It radiates signals in the horizontal and vertical planes and on the planes between them as well. If the rotation is clockwise, it is called right-hand circular, or RHC. Left-hand circular, LHC, results to a rotation that is counter clockwise.
Linear Polarization
An RFID antenna belongs to the vertically linear polarized antenna and its electric field is perpendicular to the earth's surface. An example for this type of antenna is a broadcast tower used by AM radio stations or the whip antenna mounted on an automobile. A horizontally linear polarized antenna has its electric field parallel to the earth's surface. An example is a TV antenna.
The electromagnetic waves on a linear polarized antenna propagate in one plane only, either on a horizontal plane or a vertical plane. It has the best wave propagation given that the tag orientation is fixed.
Monostatic Circular or Bistatic Circular
The mono-static antenna has only one port and is the most popular type of antenna. The transmitting signal and the receiving signal both come and go from the same port. The mono-static RFID readers can have one, two or four port readers. Some readers have five ports because an additional port (Listen Before Talk) is added.
The bi-static antenna is composed of two antennas that are connected under a common casing with two ports. The transmitted signal is processed and transmitted on one port and the received signal on the other ports. The bi-static readers have eight ports. Four ports are for transmitting and the remaining four port for receiving signals.
Tags: electromagnetic waves, linear polarized, linear polarized antenna, polarized antenna, readers have, antenna electric, antenna electric field