Compact Mobile Terminal Antenna With Endfire Circularly Polarized Beam for Satellite Communications

In this communication, a compact endfire circularly polarized (CP) antenna designed for satellite communication on mobile terminals is proposed. In our design, a rectangular loop antenna is proposed with a compressed vertical dimension which is suitable to be integrated into the plastic bezel of the mobile terminals. The folded dipole mode and loop mode of the rectangular loop antenna provide orthogonal radiation components. An L-shaped stub is introduced to excite the two modes by capacitive coupling. The directivity of the horizontally polarized (HP) radiation is improved to be comparable to that of the vertically polarized (VP) radiation when integrating with the chassis ground. Independent mode tuning can be achieved with capacitive loading on the antenna. A prototype was fabricated to validate the design. The measured results indicate that a −6 dB impedance bandwidth of 10.0%, axial ratio (AR) bandwidth of 0.76% (covering the
$S$
band of the BeiDou Navigation Satellite System (BDS) of 2483.5–2500 MHz), and a peak gain of 4.80 dBic are achieved with a compact size of
$0.47\lambda _{0} \times 0.06\lambda _{0} \times 0.004\lambda _{0}$
. The proposed CP antenna has the merits of compact size, improved gain, and quasi-planar structure which is a good candidate for mobile terminals supporting satellite communication.