Normal Mode Helical Antenna for Mobile Radio Communication

This research delves into the issue of large antennas impeding the downsizing of handheld ground sensor terminals that operate within the UHF mobile communication band. The paper introduces Normal Mode Helical Antennas (NMHAs) as a more compact option compared to traditional antennas. While previous studies have mainly focused on miniaturizing and examining the radiation characteristics of NMHAs, there is limited research on how they perform in UHF mobile communication for handheld devices. To bridge this gap, the paper presents a design and optimization approach using FEKO software. This approach includes important factors like designing a self-resonant structure, achieving input impedance matching through a tap feed method, and fabrication. Emphasizing the significance of a balun for precise input impedance measurement using a Vector Network Analyzer (VNA) is crucial due to the potential for leakage currents in NMHAs. A successfully fabricated NMHA prototype operating at 395.25 MHz, showcasing effective signal transmission and reception, has been validated for the conceptual ground terminal to satellite propagation. This study is a step forward in the advancement of miniaturized antennas for UHF communication in handheld devices, facilitating more streamlined and feasible field deployments.