Frequently asked questions: Long range identification - UHF RFID

Why is a tag/card readable only in one position?

With a linearly polarised antenna, a tag has to be directed in the same polarisation as the antenna. I.e. if the antenna is in vertical position, the tag has to be installed in vertical position as well. Horizontal orientation of a tag used with an antenna aligned vertically (and vice versa) gives a poor performance and the maximum reading distance is approximately 20-90 cm. When the reader is vertically aligned the cable is towards the floor or ceiling.

What can cause a poorer reading distance than expected? Why is a tag not read?

• Tag and reader antennas are in different polarization state. Check which reader antenna type is used: Is it linear or circular polarized? If you are using linear polarized antenna, the tag must be in the same polarization as the reader antenna. Please refer to the chapter 5 “Tags and Tag handling instructions”.
• The environment may disturb the antenna beam. The environment may disturb the antenna beam. Check that there are no metallic parts near to the reader antenna, and that there is enough free space around the antenna in order to decrease the influence of reflections.
• The antenna cable(s) is/are broken. Replace the antenna cable.
• A tag is broken or it is of type that is not supported. Check that the tag is based on Atmel’s ATA5590 (Tagidu) chip.
• The reader needs to be calibrated. Press Stop in the UHF RFID Demo software. Return to the Antenna configuration window and do the antenna configuration and calibration again.

Can I install a tag onto a metal surface? It seems that the reading distance is getting smaller?

Yes, if the tag is designed for installation on metal surface. Any UHF tag does not work on metal.