What is an RFID Antenna?

Although each system will vary in device type and complexity, each RFID system contains at least the following four components: reader, antenna, tag, and cable. The simplest systems can consist of mobile handheld RFID readers (with integrated antennas) and RFID tags, while more complex systems use multi-port readers, GPIO boxes, other functional devices (e.g., stacking lights), multiple antennas and cable to design, RFID tag and complete supporting software.

1. Introduction of RFID antenna

RFID antennas are an essential element in an RFID system because they convert the RFID reader's signal into RF waves that can be received by the RFID tag. Without some type of RFID antenna (whether integrated or standalone), an RFID reader cannot properly send and receive signals to and from RFID tags.

Unlike RFID readers, RFID antennas are passive devices that receive power from the reader. When the reader's energy is transmitted to the antenna, the antenna generates an RF field, which in turn transmits the RF signal to a nearby tag. The efficiency of an antenna to generate waves in a particular direction is called the antenna gain. Simply put, the higher the gain, the stronger the RF field and wider range the antenna will have.

RFID antennas emit RFID waves along a horizontal or vertical plane, which is described as the polarity of the antenna. If the RF field is a horizontal plane, it is described as horizontally linear, and the same principles apply to create a vertical plane RFID antenna.

The polarity of the antenna can seriously affect the read range of the system. The key to maximizing read range is to ensure that the polarity of the antenna is aligned with the polarity of the RFID tag. If these do not match, such as a vertically linearly polarized antenna and a tag with a horizontally linearly polarized antenna, the read range can be severely degraded.

Circularly polarized antennas emit waves that rotate continuously between horizontal and vertical planes to provide increased flexibility for applications by allowing RFID tags to be read in multiple directions. However, because the energy is split between the two planes, circularly polarized antennas have a shorter read range than linear antennas of similar gain.

2. The type of RFID antenna

As with most RFID devices, RFID antennas can be divided into different categories, helping to narrow down the best antenna for an application. Even though antennas are grouped by several different factors, the most common groupings for RFID antennas are polarity (circular versus linear) and ruggedness (indoor versus outdoor).