A new technique that enables passive ultra high fre- quency (UHF) radio frequency identification (RFID) tags to be read when they are placed in close proximity in an array is pre- sented. This paper demonstrates that, in a linear tag array with a tag separation of 1 cm, the interaction between the backscat- tered waves and incident wave causes a significant degradation in tag sensitivity. It is found that the use of tags that have polariza- tion diversity can improve the read performance when they are placed in close proximity to one another compared with conven- tional 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 exper- imentally 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.