Summary
International Symposium on Antennas and Propagation
2008
Session Number:2SS01A
Session:
Number:2SS01A-8
A Suggested Shape of Spirals for Expanding the Half-Power Beamwidths of UHF Band RFID’s Planar Spiral Antennae
Mayumi MATSUNAGA, Tsuyoshi MATSUOKA, Toshiaki MATSUNAGA, Yasuhiro YOKOTA,
pp.-
Publication Date:2008/10/27
Online ISSN:2188-5079
Summary:
A shape of spirals for helping to expand not only the bandwidths but also the half-power beamwidths (HPBW) of UHF band RFID’s planar spiral antennae is presented. Considering its application to UHF band’s planar spiral antennae utilized as RFID, the antennae are made to radiate fields with wide HPBW, to have wide bandwidth, to be capable of circular polarization, and as small as possible. The UHF band planar spiral antennae equipped with spirals shaped and arranged as per the way introduced in this paper have been found to be capable of radiating fields with HPBW of 120 or more degrees as well as return loss of -10 or less dB within the frequency range between 919 MHz and 966 MHz. This is a performance level far higher than that of conventional planar antennae [1], [2]. The reason for this enhancement of the HPBW and the bandwidth are because the shape of spirals has been formed differently, that is to say the spirals are now arranged like spiralling along outer surface of a cross on a plane without any grands. Therefore, the new antenna has been named "Cross Spiral Antennae (CSA)" after the shape of spirals by the authors. Despite being just changed the shape of the spirals, the HPBW and bandwidths of UHF band RFID’s planar antennae have been so greatly expanded while the size of antenna are maintained as same as that of conventional circular polarization antennae of UHF band RFID.