Modified Inverted-L Antenna With Improved Upper Hemisphere Ratio and Ground-Independent Performance for Augmented Mobile Satellite Service

High-performance satellite antennas provide high-quality communication links for mobile satellite service. Most existing research on mobile satellite antennas focuses on circular polarization (CP), frequency band coverage, and miniaturization; however, little attention is given to beam control, and an ideal satellite antenna’s beam should be directed toward the satellites or fully cover the upper hemisphere. This work proposes a simple method to enhance the upper hemisphere ratio (UHR) by modifying the traditional inverted-L antenna (ILA). A large inductor embedded in the aperture and a small capacitor loaded at the port successfully transform operation mode from the quarter-wavelength unbalanced mode to the half-wavelength balanced mode, which significantly reduces ground currents while allowing the ground to function as a reflector. Consequently, the UHR is greatly improved regardless of ground position and ground size. The antenna test and GPS reception outfield experiment are conducted under two cases with the maximum and the minimum improvement effects in a tablet environment. Significant benefits are achieved using a simple method: compare to the traditional IFA, the proposed UHR is improved by 23.4%/15.4% and the number of detectable satellites is increased by 17%–40%. Compared to the existing sky-oriented satellite antennas, the modified ILA has significant advantages of smaller size and compatibility with metal bezels.