End-fire circularly polarized antenna for satellite direct link in metal-bezel mobile terminals

Abstract Design of end-fire circularly polarized (CP) antennas on metal-bezel mobile terminals for satellite direct link poses considerable challenges. To address this challenge, we propose an end-fire CP antenna for metal-bezel mobile terminals. A metal rectangular loop antenna is placed at the top of the structure to create CP radiation. A T-shaped capacitive coupling structure is employed to improve the axial ratio (AR), while a concave slot is integrated into the T-shaped feeding network to form a matching circuit, thereby enhancing impedance matching. A prototype antenna is fabricated to validate the design. Measured results demonstrate that the antenna provides a −6 dB impedance bandwidth of 0.52 % (2,484–2,497 MHz), a 3 dB AR bandwidth of 0.85 % (2,474–2,495 MHz), and a peak gain of 2.3 dBic. Its end-fire radiation has a wide coverage beamwidth up to 103° and 44° for two principal cuts, making it suitable for the S-band of the BeiDou Satellite Navigation System (BDS). The proposed antenna features a compact design, provides ample space for future MIMO systems, and is an ideal candidate for metal-bezel mobile terminals to provide satellite direct link.