Radio frequency identification (RFID) tags are used to keep track of inventory and aid in stolen property recovery. Additional uses include paying for toll charges through automatic bank account deduction, warehouse supply management and security measures. An RFID tag antenna communicates a unique bar code back to a computer system that determines the location of the object. Passive, active and reader are the most common RFID tag antenna types.
A passive RFID tag antenna is a basic type of antenna. It works by converting a magnetic field into a power source that the tag uses to communicate. That communication signal contains the bar code or unique identifier contained within the tag. These types of antennas tend to be very cost effective and are typically disposable.
The second type is an active RFID tag antenna. Instead of just transmitting a signal, an active antenna can also receive signals. The communication process with an active RFID tag antenna is two-way. It is somewhat similar to a radio or cell phone device.
Active antennas typically communicate on certain radio frequencies. A number, such as 819MHZ, usually defines these wavelengths. The MHZ translates to megahertz. RFID tag antennas that are classified as active usually have an appearance that is similar to an extended, external cell phone antenna.
Reader or interrogator antennas are a third type. Instead of just operating on one radio frequency, these antennas have the capability of communicating on several at once. They can send and receive data just like an active antenna. Some of these antennas are actually made up of several antennas rather than just one.
Each RFID tag has the capability of communicating on high, low, very high, or ultra high frequencies. The different frequencies can be thought of as being similar to separate radio stations. When turned to a certain frequency, a radio is able to receive communication from certain channels.
During the communication and data exchange process, RFID tags send and receive signals in a variety of manners. Linear polarization transmits an electromagnetic signal in one vertical or horizontal line. Circular polarization sends and receives signals in two vertical or horizontal lines. These signals often travel in a circular motion.
The use of RFID technology in retail and other commercial environments is controversial. It can be a cost effective means of electromagnetic tracking, but it also raises several privacy issues. While the technology does make certain transactions more convenient, transmitting personal information through radio frequencies puts it at risk of exposure to unwanted parties. The use of RFID technology opens up the door to potential spying activity.