A dual-frequency circularly polarized satellite navigation antenna for embedding in mobile terminals

Traditional dual-frequency circularly polarized antennas have characteristics such as being external, heavy due to dielectric loading, and large in size, making them difficult to embed in mobile terminals. Currently, satellite navigation antennas in mobile terminals mostly use linear polarization, which fails to meet the high standards of positioning accuracy required by users. Therefore, this paper presents a dual-frequency circularly polarized satellite navigation antenna that can be embedded in mobile terminals. This antenna consists of L1 and L5 band antennas, both employing a coupled feeding method. A U-shaped slot is created between the feeding point and the antenna, allowing the antenna to function as an LC resonator. By adjusting the width of the slot, we can control the capacitance, thereby achieving good impedance matching. Additionally, adjusting the size of the ground plane effectively controls the current direction between the antenna and the feeding microstrip line. The antenna primarily provides horizontal current, while the feeding microstrip line mainly delivers vertical current, significantly enhancing the circular polarization reception characteristics of the antenna. Measured results show that the maximum gains for the L1 band antenna (Ant.2) and the L5 band antenna (Ant.1) reach 3.34 dBic and 3.66 dBic, respectively, with axial ratios (AR) less than 3 dB in their respective frequency bands. These results indicate that the antenna features low cost and compactness, while demonstrating excellent performance in dual-frequency circular polarization.