RFID System antenna description

The antennas of RFID systems generally include reader antennas (Reader Antenna) and tag antennas (Tag Antenna). The function of the reader-writer antenna is to emit electromagnetic waves, activate tag work, realize data communication with the tag, and at the same time receive the electromagnetic waves reflected back by the tag, and pass them to the lower-level module of the receiver for data demodulation and processing. The position of the recognized object in space is generally not fixed, and the placement of tags is also arbitrary. Coupled with other uncertain factors, the reader antenna needs to meet omnidirectional performance. The use of circularly polarized antennas can To avoid the situation where the recognized object cannot be recognized by the reader due to the change of polarization direction when the spatial position changes, secondly, the reader antenna also needs to meet the performance of low proFile and miniaturization.

The function of the tag antenna is to receive the electromagnetic waves emitted by the reader and send the required data back to the reader to achieve mutual communication. In addition to realizing the electromagnetic wave transceiver function, the passive tag antenna also needs to serve as an energy collection device for the tag. The chip provides the energy. There are numerous requirements for tag antenna design. First of all, the tag needs to be able to be attached to the object being identified, which determines that the size of the tag must be small. Since the size of the chip is small enough, it can basically meet the needs of various applications. Therefore, the size of the tag antenna basically determines the overall size of the tag. , the tag antenna should meet the design requirements; secondly, in most cases, due to the random placement of tags, each application scenario requires the direction of the tag antenna to be omnidirectional or hemispherical, so that it can communicate with the reader and writer at all angles. For reliable communication; thirdly, the IC chip in the tag is specially developed, and its own impedance has no specific standard. Compared with the tag antenna, the cost of chip development is much higher. Therefore, in general, the design of the tag antenna is The impedance transformation is carried out in order to achieve co-drive matching with the specific chip, thereby providing maximum energy for the tag chip operation; finally, in order to meet the large-scale application of tags, the tag antenna should be low-cost, simple to process, and easy to mass-produce manufacture. "

The basic radiation principle of electromagnetism states that the size of a radiation source is generally proportional to its operating wavelength, which means that the lower the operating frequency of the antenna, that is, the longer the operating wavelength, the larger its overall size will be, and vice versa. This shows that in terms of miniaturization, high-frequency electronic tags have huge advantages. In addition, a higher operating frequency will make the antenna more directional and gain higher, but its wavelength range will also be narrower. In short, when designing an RFID system antenna, it is necessary to comprehensively consider various application requirements and finally design an antenna suitable for its application scenario.