RAIN RFID Reader Sensitivity Testing – WG Publication Exec Summary

Blog summary
RAIN RFID Reader Sensitivity Testing – WG Publication Exec Summary elaborates why readers may become the limiting elements for the read range of RAIN RFID systems and what this means for reader selection.

RAIN RFID systems consists of two essential parts: the reader and the tags. For a lengthy period of time RAIN RFID’s existence, the power consumption of a tag was the limiting factor for the achievable communication range in a RAIN RFID system.

Around five years ago, tag and tag chip design made enough progress that new constellations came up. Instead of the power from the reader to the tag, the power from the tag to the reader became more important and was the limiting factor of a RAIN RFID system. The RAIN Alliance decided to address this topic and developed a whitepaper on RAIN Reader Sensitivity and published its first version in 2016 followed by the second version in 2021 (see rainrfid.org/resources/).

The whitepaper on RAIN RFID Reader Sensitivity Testing describes the considerations to address on reader sensitivity. While the power coming from the tag is indeed critical, the key topic from a reader’s viewpoint is the receiver sensitivity in dependence on various parameters. The key parameters identified are:

Self-jamming: Disturbance caused by reflection due to large (usually metal) objects near the antenna, or the degenerated antennas themselves.
Link frequency: Variation of the BLF (Back Link Frequency) due to tag design, production or environmental conditions (e.g., operating temperature).
Signal phase: Variation of tag signal in dependence on even small distance variations due to wave propagation physics.

The RAIN Alliance’s target is a simple, repeatable, and verifiable test that can be applied consistently to all readers. The RAIN Alliance’s work was a major contributor for the standardization. For example, ISO/IEC 18046-2 now covers the requirements of the RAIN Alliance, and the whitepaper emphasizes that the reader receiver performance test shall be done according to this ISO/IEC 18046-2 standard.

The defined test delivers a clear reader receiver sensitivity result defined for a read success rate of 90% over various parameters, suitable for reporting in datasheets. The quantification of the reader sensitivity over the specified parameters allows system designers to select readers fitting to the tags in order to ensure that the reader receiver’s performance meets the application requirements. The recommended parameters for variation are BLF +/- 10%, tag signal phase 0-180° and return loss from 0 to 15 dB over for at least 8 phases.

Finally, the test results will deliver a reader receiver sensitivity over operating frequency, BLF, tag signal phase and self-jamming between -45 dBm for budget readers, -70 dBm for typical readers, and beyond -85 dBm for high-end devices. All these measurement activities lead to a RAIN RFID system operating on an appropriate performance level to ensure a high market acceptance of the technology. Learn more here.