Therefore, for the circular polarization antenna for
UHF bandwidth RFID reader designed for this study,
in order to exactly recognize a few tags
simultaneously without errors in the distance, original
signals were separated into two signals with phase
difference of 90o using Hybrid Coupler (insert loss:
0.16dB), and each of them were provided to two Strip
line antennas with a length of λ/2. Then, to realize a
circular polarization using the two signals with phase
difference of 90°, this study designed reflection plate
(cross section: 13.4cm2) with two feed points doubly
to maximize radiation efficiency of the antenna,
which significantly improved reception which is one
of important parameters of RFID system.
Section 2 describes design of a reader antenna;
Section 3 describes the measurement and analysis;
and Section 4 concludes this study