A novel broadband circularly polarized stacked patch antenna is proposed for Chinese UHF radio frequency identification (RFID) reader/writer applications.The antenna is composed of two corner truncated patches and an S-shaped horizontally meandered strip (HMS)

all of which are printed on the upper side of the FR4 substrates.One end of the S-shaped HMS is connected to the main radiating patch by a probe

while the other end is connected to an SMA connector.Using the proposed S-shaped HMS feed technique

a good impedance matching and symmetrical broadside radiation patterns can be achieved.Simulation results are compared with the measurements

and a good agreement is obtained.The measurements show that the antenna has an impedance bandwidth (VSWR＜1.5) of about 26.6% (722-944MHz)

a 3dB axial ratio (AR) bandwidth of about 10.8% (838-934MHz)

and a gain level of about 8.5dBi or larger within the 3dB AR bandwidth.Therefore

the proposed antenna can be a good candidate for UHF RFID readers/writers operating between 840 and 928MHz.