Briefly describe several important requirements in the design of UHF RFID tag antennas

There are several important requirements in the design of RFID tag antennas, which mainly depend on the application of the tag. These design requirements also determine the standards for selecting RFID tag antennas.

1. UHF RFID tag antenna frequency band

The operating frequency band of the antenna mainly depends on the regulations of the tag frequency used in that country or region. For example, the operating frequencies of ultra-high frequency RFID tags specified in China are 840.5~844.5MHz and 920.5~924.5MHz.

2. Shape and size of UHF RFID tag antenna

The shape and size of the antenna must be able to smoothly embed or attach the label to the designated target, and also suitable for printing the label. For example, cardboard boxes or cartons, airline luggage tags, identification cards, etc. That is to say, the shape and size of the antenna mainly depend on the usage and application environment of the tag.

3. UHF RFID tag antenna recognition range

The minimum recognition range of tags is usually determined by three factors, namely effective radiated power (EIRP), target, and directionality. Among them, the effective radiation power is usually determined by the rules of the country or region. For example, China stipulates that the EIRP used for UHF RFID is 3.2W. The performance of the tag varies depending on the target it is placed on, or its performance may also be affected when other objects approach the tag. The design of tag antennas should minimize the sensitivity of tags to different targets or environments as much as possible, and optimize the performance of tags. The recognition range also depends on the directionality of the tag antenna, and some applications require the tag antenna to have a specified directional pattern, such as omnidirectional or hemispherical coverage.

4. Mobile application requirements for UHF RFID tag antennas

Consider a scenario where objects labeled with RFID tags may be in trays or cardboard boxes, transported by conveyor belts at a speed of 200m/min. In this case, the Doppler shift of an RFID system operating at 915MHz is less than 30Hz, which usually does not affect the operation of the RFID system. However, tags consume less time within the recognition range of the reader, so RFID systems are required to have high-speed reading capabilities. In this situation, it is necessary to carefully design the RFID system in order to reliably identify moving tags, which also puts higher demands on tag antenna design.

5. Reliability requirements for UHF RFID tag antennas

RFID tags are reliable devices that can withstand external conditions such as temperature, humidity, and pressure, and are not damaged during tag insertion, printing, and stacking. So in antenna design, it is also required to consider the influence of these factors