Reduction of Proximity Effects on UHF Passive RFID Systems by Using Tags with Polarization Diversity

Qi Zhang, Michael J. Crisp, Richard V. Penty, Ian H. White

Research output: Contribution to journalArticlepeer-review

11 Citations (SciVal)


A new technique that enables passive ultra high frequency (UHF) radio frequency identification (RFID) tags to be read when they are placed in close proximity in an array is presented. This paper demonstrates that, in a linear tag array with a tag separation of 1 cm, the interaction between the backscattered waves and incident wave causes a significant degradation in tag sensitivity. It is found that the use of tags that have polarization diversity can improve the read performance when they are placed in close proximity to one another compared with conventional linear tags. Two ways of achieving polarization diversity are studied in this paper, namely: 1) using a circularly polarized tag and 2) using a cross-polarized tag pair. Both methods show an improvement in close proximity read performance and it is experimentally demonstrated that by using cross-polarized tag pairs in an array, one achieves on average a 2.6-dB increase in read power margin for a 57-tag array with 1 cm separation compared with using conventional linearly polarized tags.

Original languageEnglish
Article number7042269
Pages (from-to)2264-2271
Number of pages8
JournalIEEE Transactions on Antennas and Propagation
Issue number5
Early online date13 Feb 2015
Publication statusPublished - 1 May 2015


  • Circularly polarized tag
  • close proximity
  • passive ultra high frequency (UHF)
  • polarization diversity
  • radio frequency identification (RFID)
  • tag pairs

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Electrical and Electronic Engineering


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