“Axial Ratio in circular polarization RFID Antenna, measured by major axis to minor axis ratio, determines the no. of tags that can be read within the range, by the reader.”
Radio-frequency identification (RFID) technology has revolutionized various industries by enabling efficient tracking, monitoring, and management of assets. As the use of RFID Technology is proliferating across multiple sectors, retail, supply chains, and healthcare in particular, RFID implementation requires technical know-how regarding how businesses can get the best of RFID technology.
RFID systems consist of tags and readers, and the performance of these systems heavily relies on the antennas being used. While implementing an RFID system in applications where an RFID Antenna is to be used with a Fixed RFID reader, understanding the technical properties of the antenna becomes crucial. Axial ratio is a crucial parameter in RFID antennas, especially in circular polarized antennas, as it directly impacts the system's performance. Other factors include the power gain of the RFID antenna, size, frequency, and polarization.
Axial Ratio in an RFID Antenna
The axial ratio in an RFID antenna refers to the ratio of the major and minor axes of the radiation pattern. It determines the antenna's ability to maintain polarization purity, particularly in circular polarized antennas.
A low axial ratio signifies a more circularly polarized radiation pattern, which is desirable in many RFID applications. Circular polarization allows the tags to be read regardless of their orientation, thus improving the overall system reliability and read range.
Ideally, being a ratio, Axial Ratio doesn’t have a measurement unit but it is typically measure in decibel (dB) as it expresses the ratio of major axis and the minor axis of radiation on a logarithmic scale. For circular polarized antennas, AR closer to 0 (zero) is better.
Axial Ratio in Circular Polarized RFID Antenna
Currently, circular polarized antennas are the most used RFID antennas in the world. In circular polarized RFID antennas, the axial ratio plays a critical role in ensuring consistent tag readability. Various RFID systems require the axial ratio of RFID antennas to be lower for optimal performance in conditions where the orientation of the RFID tag concerning the reader and antenna is random.
In RFID Antennas, Circular Polarization is achieved by generating two orthogonal linear polarized fields with a 90-degree phase difference, unlike linear polarization where the unidirectional signal is transmitted. The axial ratio here measures how close the antenna's radiation pattern is to a perfect circle. A lower axial ratio indicates a more circularly polarized field, which is advantageous in RFID systems as it minimizes the impact of tag orientation on read performance.
Factors to Consider while Selecting an RFID Antenna
While selecting an RFID Antenna, choosing a low axial ratio antenna is the best option but there are some other factors that one must consider as well:
1. Frequency of the RFID Antenna
2. Polarization of the RFID Antenna
3. Size of the RFID Antenna
4. Gain of the RFID Antenna
Typically, Small low axial antennas are of low gain. Large antennas have higher input impedance and small-sized low axial ratio antennas have lower input impedance and offer low resistance to the energy coming from the reader.
Low axial antennas can also be used with other RFID antennas operating on the same frequency range as low axial antennas have lower output impedance than a linear antenna with the same input impedance. It allows it to work with other RFID antennas.
Advantages of Low Axial Ratio in RFID Antennas for Business Applications
The low axial ratio in RFID antennas offers several advantages in various business applications. It enhances read reliability by reducing the sensitivity to tag orientation, leading to more accurate and consistent data capture. It is particularly beneficial in retail inventory management, where quick and accurate scanning of tagged items is crucial for maintaining optimal stock levels and preventing stock-outs. Similarly, in healthcare, the low axial ratio of RFID antennas being used in RFID systems ensures that medical supply tracking, patient tracking, staff tracking, access control, etc. work efficiently without failure.
Moreover, in large warehouses, receiving docks, and logistics business applications, RFID Antennas with low axial ratios offer efficient, more tag detection over the entire coverage and ensure efficiency with given power output from the RFID reader.
There are various RFID Antennas available in the market that offer low axial ratios of 1dB, 1.5dB, 2dB, etc. Low axial ratio antennas improve read range and penetration, making them suitable for applications in logistics and supply chain management, where reading tags through densely packed items or from a distance is essential for operational efficiency.
9dBi circular polarized antennas with 2dB Axial Ratio are very popular in RFID systems being used in warehouses, retail inventory control, POS operations and supply chains.
Some Antennas with Low Axial Ratios
Several antennas in the market exhibit low axial ratios, making them suitable for RFID applications requiring high reliability and performance.
For instance, the Circularly Polarized RFID Antenna AN480 from Zebra Technologies boasts a remarkably low axial ratio of 1.5 dB, ensuring consistent tag detection and read accuracy. Similarly, the 8.5 dBi-Gain Circular Polarized RFID Antenna, the Zebra AN510 features an axial ratio of 1.0 dB, making it ideal for demanding RFID applications in industrial and outdoor environments.
To conclude, the axial ratio is a crucial parameter in RFID antennas, especially in circular polarized antennas, as it directly influences the system's performance. Low axial ratio antennas offer enhanced reliability, read range, and penetration, making them invaluable in various business applications such as retail, logistics, and supply chain management.
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