How many RFID tags can a UHF tag reader follow at once?

RFID (Radio Frequency Identification) is a technology that uses radio waves to identify and track objects. RFID tags are small devices that can be attached to or embedded in objects, and RFID readers are devices that can communicate with RFID tags and read their data. RFID tags can be classified into two types: passive and active. Passive RFID tags do not have a battery and rely on the reader’s signal to power up and respond. Active RFID tags have a battery and can transmit their own signal.

UHF (Ultra-High Frequency) is a range of radio frequencies between 840 MHz and 960 MHz. UHF RFID tags and readers operate in this range and offer several advantages over other RFID frequencies, such as longer read range, faster data transfer, and higher tag capacity. However, UHF RFID also faces some challenges, such as interference, attenuation, and reflection.

How many RFID tags can a UHF tag reader follow at once?

The number of RFID tags that a UHF tag reader can follow at once depends on several factors, such as:

• The protocol: The protocol is the set of rules and commands that govern the communication between the reader and the tags. Different protocols have different capabilities and limitations in terms of tag capacity, collision avoidance, and anti-collision algorithms. For example, the EPC Gen2 protocol, which is the most widely used protocol for UHF RFID, can support up to 1,000 tags per second1.

• The reader: The reader is the device that generates the radio signal and receives the tag responses. Different readers have different specifications and performance in terms of power output, antenna gain, frequency range, modulation scheme, data rate, memory size, processing speed, and software features. For example, the ST25RU3993 reader IC from STMicroelectronics can support up to 1,500 tags per second with its high-performance ASIC radio technology2.

• The tag: The tag is the device that stores the data and responds to the reader’s signal. Different tags have different characteristics and performance in terms of chip type, memory size, data rate, encoding scheme, modulation scheme, backscatter power, sensitivity, antenna design, and orientation. For example, the ST25DV-I2C tag from STMicroelectronics can support up to 53 kbps data rate with its fast transfer mode3.

• The environment: The environment is the physical setting where the RFID system operates. Different environments have different effects on the radio signal propagation and reception, such as interference, noise, reflection, absorption, multipath fading, polarization mismatch, etc. For example, metal surfaces can reflect or block the radio waves, while liquids can absorb or attenuate them.

Therefore, there is no definitive answer to how many RFID tags a UHF tag reader can follow at once. It depends on the combination of these factors and their trade-offs. However, some general guidelines are:

• The higher the frequency, the shorter the wavelength, the smaller the tag antenna size, and the higher the tag density.

• The higher the power output of the reader, the longer the read range of the tags.

• The higher the antenna gain of the reader or the tag, the longer the read range of the tags.

• The higher the data rate of the reader or the tag, the faster the data transfer between them.

• The lower the collision probability between tags or between readers, the higher the tag capacity.

Conclusion

UHF RFID is a technology that uses radio waves to identify and track objects. UHF RFID offers several advantages over other RFID frequencies, such as longer read range, faster data transfer, and higher tag capacity. However, UHF RFID also faces some challenges, such as interference, attenuation, and reflection. The number of RFID tags that a UHF tag reader can follow at once depends on several factors, such as protocol, reader specifications performance , tag characteristics performance , and environment effects . There is no definitive answer to this question but some general guidelines can be followed.