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RFID Antennas - How to Choose?

RFID Antennas - How to Choose?

Issue Time:2022/08/24
The RFID antenna transmits power from the RFID reader in the form of radio waves to the RFID tags within its range. If the reader is the brain of an RFID system, then the antennas are its arms, which transmit and receive information between the RFID tag and the reader. RFID antennas usually look similar. What makes them different are the physical specifications. When choosing an antenna, several parameters should be considered, such as frequency range, magnification, opening angle/beamwidth, and polarization.

Frequency range

Each country has regulations that define acceptable UHF/RFID frequencies. The three most common ranges for UHF RFID antennas are:

865-868 MHz (EU/ETSI,

902-928 MHz (US/FCC),

860-960 MHz (worldwide).

When choosing an RFID antenna, choose the frequency range of its working area.

Zoom in and open angle

Magnification and opening angle (also called beamwidth) are closely related. The greater the amplification (gain), the narrower the radio waves, which means that the area covered is also narrower, but the beams reach farther. All in all, magnification affects the width of the wave. The greater the magnification, the more concentrated the waves. It can easily be represented as stronger and weaker flashlight beams. The choice of the ideal antenna depends on the solution. If we have a lot of tags nearby, the best option is to zoom in on a smaller antenna with a wider beam.

Polarization

Most RFID UHF antennas are circularly or linearly polarized. This means that linearly polarized antennas emit radio frequency waves on a horizontal or vertical level. A circularly polarized antenna transmits waves in a clockwise or counterclockwise circular motion. In this case, we distinguish between left circular polarization (LHCP) and right circular polarization (RHCP). If we have a configuration with multiple or multiple antennas pointing towards each other, it is important to know if they are LHCP or RHCP. Circular antennas of the same polarization can overlap. Using opposite circularly polarized antennas will allow the creation of a more efficient reading area.

Circular and linear polarization: which antenna is right?

The choice between circularly polarized and linearly polarized antennas can significantly impact the RFID solution.

Linear polarization occurs when an electromagnetic wave travels on one level (horizontal or vertical). Linearly polarized antennas are the best choice when all RFID tags are located in the same direction and at the same height. Due to the concentrated transmission, linear antennas generally have a larger read range than circular antennas with the same magnification.

Omnidirectional antennas are more suitable for solutions where we cannot predict the position and orientation of RFID tags. They emit waves that resemble two-dimensional spiral motion. Because omnidirectional antennas lose power in two dimensions, they have a shorter read range compared to linear antennas.

When deciding on the type of antenna used in an RFID system, a key factor is understanding how the antenna works and how the RFID tag is oriented relative to the antenna.

Types of RFID antennas

Small and large RFID antennas

Antennas come in different sizes, from cell phones to TV sizes. The difference in size usually points to the read range. The larger the antenna, the longer the read range and vice versa. Mounting location may also affect antenna selection. Some installation locations do not allow the use of large antennas due to space constraints or purely aesthetic reasons.

Internal and external RFID antennas

Because RFID can be implemented in nearly all environments, elements of the system can be designed to work in the presence of water and dust. All electronic components are certified against water and dust according to the US IEC 60529 specification and UK EN 60529, ranging from IP 00 to IP 69. Operating temperature should be considered when deciding whether to operate an antenna outdoors or indoors. Antennas have a specified temperature range for optimal operation. Outside this range, the antenna may work slowly or stop working completely.

Integrated and non-integrated RFID antennas

The antenna can be integrated into a chassis with the RFID reader, purchased as a unit, or work alone. Integrated devices help save space and build more mobile systems without worrying about cables. This solution may be the best choice for retail and distribution, as it is generally small, easy to use, and more visually appealing than two inconvenient external devices. On the other hand, external antennas offer more configuration possibilities and flexibility when it comes to different uses.

The above briefly introduces RFID antennas. If you want to buy RFID readers, antennas, or tags, please contact us.

Yanzeo is a professional custom RFID equipment manufacturer. The company has invested heavily in scientific research projects in the field of automatic identification all year round. PDA, RFID reader, and other barcode RFID-related products produced by SR series have successively passed the US FCC certification, EU CE certification and ISO9001:2008 quality management system certification. Widely used in government agencies, public security, public utilities and logistics supermarkets, property security, etc.
Yanzeo R781 6m Long Range integrated UHF reader, 8dbi Antenna USB RS232 RS285 RS485 Outdoor IP67
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