A wideband endfire CP antenna using magnetic dipole

This paper presents a wideband circularly polarized (CP) antenna with high gain and end-fire radiation. The antenna consists of two metal strips on the same side of two substrates separated at a distance of 0.09λ
_g
, where λ
_g
is the guide wavelength at the lowest operating frequency. The two metal strips are shorted together at three edges. Two pairs of tapered stubs are protruded from the metal strips to generate two resonances and two orthogonal electric fields with 90°-phase difference, resulting in a wideband CP antenna. Simulation results show that the antenna has a wide impedance bandwidth (IMBW) of 2.31-4.00 GHz (53.6%) for S
₁₁
<;-10 dB and axial-ratio bandwidth (ARBW) of 2.30-3.81 GHz (49.4%) for AR<;3 dB. Stable endfire radiation is observed over the operating bandwidth with a peak gain of 7.83 dBi. The antenna is a good candidate for uses in radio frequency identification (RFID) readers to cover the ISM band.