Compact Crossed Dipole Antenna With Meandered Series Power Divider for UHF RFID Tag and Handheld Reader Devices

A low-profile and meandered crossed dipole antenna design for ultrahigh-frequency (UHF) radio-frequency identification (RFID) circularly polarized (CP) tag or handheld reader application is described in this communication. The crossed dipole CP condition is obtained by employing a series power divider meandered at the center of the dielectric substrate, and a surrounding ring which acts as a T-match network guarantees impedance matching. The series power divider alleviates the problem of using a balun when the crossed dipole is fed with a 50 Ω coaxial cable. A prototype has been manufactured on a 56 × 56 × 0.4 mm
³
FR4 dielectric substrate, and the measurement results show a S11 ≤-10 dB bandwidth of more than 14.4% (865.6-1000 MHz), an axial ratio (AR) 3 dB bandwidth of 2.8% (906-932 MHz) which can essentially cover the Federal communications commission (FCC) UHF RFID band, and a broadside RHCP peak gain of 1.4 dBic at 919 MHz. When the antenna is connected to an RFID tag chip, excellent read range performance within the whole 902-928 MHz bandwidth has been demonstrated (with maximum values of 7 and 9.9 m when interrogated with a linearly polarized and a CP reader antenna, respectively).