RFID antenna classification

RFID Antenna is a vital part of hardware equipment in RFID reading. The difference of antenna directly affects the reading distance, range, etc.; there are many kinds of RFID antennas, how to choose the appropriate antenna according to different projects is very important, the following is a point Talking from experience

1. According to different materials:

There are PCB antennas, ceramic antennas, aluminum plate antennas, FPC antennas, etc. Each material has its advantages and disadvantages, and the use scenarios are also different; such as ceramic antennas, the performance is stable and the size can be miniaturized, and the smallest known one can be made Up to 1818mm, of course there may be smaller ones, but ceramic antennas are not suitable for making them very large. The largest on the market is only 6dbi, with a size of 120*120mm. No matter how large it is, it is not as good as PCB and aluminum boards in terms of production and cost. PCB antennas and aluminum plate antennas are relatively common choices for high-gain antennas. They can be used outdoors with a casing, but the performance of different batches of PCBs may vary; the biggest feature of FPC antennas is flexibility, which is suitable for almost all small electronics.

2. The difference between circular polarization and linear polarization antenna

For linear polarization, when the polarization direction of the receiving antenna is consistent with the direction of the linear polarization (electric field direction), the induced signal is the largest (the projection of the electromagnetic wave in the polarization direction is the largest); with the polarization direction of the receiving antenna When the deviation from the linear polarization direction increases more and more, the induced signal becomes smaller (projection decreases); when the polarization direction of the receiving antenna is orthogonal to the linear polarization direction (magnetic field direction), the induced signal is Zero (projected to zero). The linear polarization method has higher requirements on the direction of the antenna. There are few applications of linearly polarized antennas. For example, the antennas in microwave anechoic chamber experiments must be linearly polarized antennas.

For circularly polarized antennas, no matter what the polarization direction of the receiving antenna is, the induced signal is the same, and there will be no difference (the projection of electromagnetic waves in any direction is the same). Therefore, the use of circular polarization reduces the sensitivity of the system to the orientation of the antenna (the orientation here is the orientation of the antenna, which is different from the orientation of the aforementioned directional system). Therefore, circularly polarized antennas are used in most of the IoT projects.

3. The difference between near field antenna and far field antenna

As the name suggests, the near-field antenna is an antenna for short-distance reading. The energy radiation is concentrated and restricted in the relatively short range directly above the antenna, which ensures the short-distance reading effect without misreading or cross-reading the surrounding electronic tags. Its application is mainly aimed at projects that require short-distance reading without misreading tags around the antenna, such as Jewelry inventory management, medical device management, unmanned supermarket settlement, smart Tool cabinets, etc.

The far-field antenna has a large energy radiation angle and a long distance. As the antenna gain increases, the larger the size, the radiation range and reading distance increase accordingly. In terms of applications, all applications involving long-distance reading require far-field antennas, and handheld devices also use far-field antennas, such as warehousing and logistics management, factory material control, Asset inventory, etc.