What is the difference between Circular polarization antennas or near field antennas?

What is the difference between Circular polarization antennas or near field antennas?

  • 2020/12/25

Radio frequency identification (RFID) technology is a very important part of the IOT. The antenna used in the RFID system reader is one of its most important equipment. RFID antennas for far-field applications usually use high-gain circularly polarized antennas or antenna arrays to increase their reading distance. Near-field RFID reader/writer antennas require a strong magnetic field, wide frequency band and low gain.

Circular polarization is a classic antenna type. The biggest advantage is that it still has better performance in severe weather. This kind of antenna is widely used in radio frequency identification, there are many types, and the technology is relatively mature. Wide-band and multi-band circularly polarized antennas, antenna arrays are beginning to receive attention in RFID systems, especially circularly polarized antenna arrays, because the antenna array has high gain characteristics, which can greatly increase the identification distance of the antenna.

RFID near field antenna is a new type of antenna proposed in recent years, the near-field antenna of UHF band has the advantages of long distance, miniaturization, and strong anti-interference ability.The RFID near-field antenna is different from the general far-field antenna. It does not pay attention to the far-field gain and pattern, but pays more attention to the direction and strength of the short-range magnetic field. The near-field antenna generates a strong and uniform magnetic field, which can ensure a longer effective reading target distance.

Performance index of circular polarization antenna

In far-field conditions, circularly polarized antennas are usually used as reader antennas, and linear polarized antennas are used as tag antennas.In order to increase the reading distance, RFID systems usually use high-gain circularly polarized antennas or antenna arrays. Performance mainly includes input impedance, S-parameter, gain, shaft ratio, etc. For a circularly polarized antenna array, the total gain of the antenna array, the gain of each unit and the isolation between units are also important indicators.

Performance indicators of RFID near-field antennas

On RFID near-field antennas, the main focus is on the magnetic field distribution in the near area.

Design antennas according to different application requirements to produce different magnetic field distributions. The far-field antenna focuses on characteristics such as pattern and axial ratio. Near-field antennas mainly focus on S-parameters, input impedance, current distribution, and near-field magnetic field distribution.

The readability of the tag is tested at different angles and distances of the antenna magnetic field. In this way, the reading range of the antenna at different distances and angles can be judged. In view of the different properties of the far and near fields, it is sometimes necessary to use a variety of tags for testing. These tags are basically divided into three categories, including far field tags, near field tags, far & near field tags.

Founded in 2009, Hopeland is a trusted source in the RFID hardware industry.Our antenna original appearance designed high-end UHF RFID Antenna, high gain but low standing-wave ratio brings best performance. Engineering plastic housing, rugged construction, high protection level for wide using with UHF RFID reader, such as assets tracking, warehouse management, intelligent traffic management, vehicle tracking, production line management, intelligent weight measurement etc. Our product passed CE, FCC, CCC, SRRC and series of certificates. With core advantages of long reading distance, excellent multi-tag reading, advanced anti-collision algorithm, various communication interfaces, different operation systems &SDK choices, industrial level, our devices are widely used in areas of ETC, Intelligent Parking, Airport, Smart New Retail, Smart Grid, Assets Tracking, Warehousing& Logistic, Supply Chain, Industry 4.0 and so on. At the same time, the generated magnetic field should be evenly distributed to avoid missing reading.

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