A Miniature High-Gain Low-VHF Antenna

This paper presents a miniature antenna design for practical applications in wireless low-power low-VHF communications. The proposed antenna is designed to achieve a high gain for a given size (41 cm x 30 cm x 20 cm including a ground plane). To design the electrically small and efficient antenna, closely-spaced multiple short monopoles, radiating fields that are in phase, are introduced. The in-phase radiation is enabled by an efficient, shared phase shifter which is formed by a capacitive load and air-core coils connected to each short monopole. A prototype optimized for a small ground robotic platform is designed and fabricated. Performance characterization based on simulation analysis and outdoor measurements demonstrates that the proposed approach allows for a higher gain yet more compact low-profile antenna compared with recently developed low-VHF antennas.