Axial-Ratio Bandwidth Enhancement of Circular-Polarized Bezel Antennas Using a Parasitic Capacitive Strip for Mobile Satellite Communications

In this communication, a compact circularly polarized (CP) antenna with enhanced axial-ratio (AR) bandwidth is proposed for mobile satellite communications. This antenna utilizes a tri-dipole configuration deployed on the upper bezel of a mobile terminal with a small clearance. Due to the small distance to the mainboard, the radiation pattern of the dipole is deformed caused by the inbalanced currents on the two arms. To solve this problem, a capacitive balun is integrated with the dipole to co-direct the currents on the dipole and correct the radiation pattern. This balun structure also enhances the AR bandwidth while preserving the integrity of the main board. The fabricated prototype shows a 3 dB AR bandwidth of 195 MHz and a −6 dB impedance bandwidth of 360 MHz at 3.8 GHz within the clearance of 0.5 mm. Due to the merits of compact size, wide bandwidth, and balancing capability, the proposed antenna architecture is suitable for mobile terminal applications of satellite communications, demonstrating significant potential in space-constrained systems.