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Study of Multi-band Antenna Designs for Marine Communication and Ocean Monitoring

Year: 2025
Type: dissertation
Abstract: Monitoring the ocean environment is essential for understanding climate change, protecting marine biodiversity, and enabling sustainable exploitation of marine resources. Human activities such as oil spills and overfishing have significantly disrupted oceanic ecosystems. As a result, there is increasing interest in monitoring marine environments and tracking the health of aquatic species to identify signs of ecological stress. However, acquisition of data from oceans has been a challenging and expensive task. Marine environment lacks adequate communication infrastructures, and traditional solutions such as monitoring ships and underwater cable networks remain prohibitively expensive and logistically complex. These limitations underscore the need for low-cost, scalable, and autonomous ocean monitoring systems. The internet of sea (IoS) concept, which is a low-cost marine Internet of Things (IoT) network, provides a promising alternative. These systems are envisioned to comprise low-power sensor nodes embedded in animal tags and surface-level communication relays such as floating buoys, to the best knowledge of us. While few marine IoT systems have been proposed in literature, their antenna designs are often repurposed from terrestrial use and fail to meet the stringent demands of the ocean environment. The frequency bands, size constraints, and seawater isolation call for novel marine purpose-designed antennas with tailored mechanical and electromagnetic characteristics. In this dissertation, we first propose a high-performance antenna system designed for oceanic communication buoys. These buoys can form a mesh network that relays data across long distances. Operating at both the 900 MHz Long Range (LoRa) and 2.4 GHz Bluetooth Low Energy (BLE) bands, the dual-band microstrip antenna array for the horizontal communication exhibits high aperture efficiencies for both bands, with a very low profile. The dual-array antenna module, on top of the buoy, has six such dual-band linear arrays to form a hexagonal sectorial array architecture. Besides, to enable global positioning and synchronization, a high-gain circularly polarized Global Positioning System (GPS) antenna array is mounted on top of the hexagonal dual-array antenna module. We design a sequentially rotated right-hand circularly polarized (RHCP) microstrip array that leverages aperture efficiency through a compact, sequentially rotational feeding configuration. This design is optimized to meet the spatial and gain requirements while performing the highest aperture efficiency for similar state-of-the-art designs. The marine animal sensor tag, as another critical component of the Internet of Sea system, supports biological monitoring by recording data directly from aquatic species. Two types of antenna are required: the first is a built-in multi-band electrically small (ES) antenna for animals that frequently breathe on sea surface, and the second is a pop-up deployable antenna that can be tightly coiled during underwater operation and later extend above the sea surface upon release. ES antennas inherently struggle to achieve wideband operation due to fundamental physical limits. Furthermore, the existing literature lacks design methods for multi-band fully ES antennas. We propose a practical design method for a multi-band ES antenna, which is the first quad-band fully ES antenna, to the best of our knowledge. In addition, a new deployable antenna is proposed for archive marine animal tags. Specifically, we employ shape memory alloy (SMA) wire that allows the antenna structure to mechanically unfold at room temperature and elevate upon current heating. This mechanism not only lifts the antenna above the water surface but also extends antenna size, improving both gain and antenna height. Such adaptive mechanical-electromagnetic co-design remains largely unexplored in prior studies, and our proposed antenna is, to the best of our knowledge, the first deployable antenna for such a marine IoT network. In conclusion, this dissertation addresses critical antenna design challenges for IoS system. By developing multiple innovative antennas—including dual-band microstrip antenna arrays and RHCP GPS antenna arrays for floating communication buoys, multi-band electrically small antennas for compact marine animal tags, and SMA-actuated deployable antennas for improved long-range communication—this work substantially advances the state of the art in marine IoT communication. The solutions proposed here lay a strong foundation for future research and practical deployment, paving the way toward more scalable, cost-effective, and comprehensive ocean monitoring systems.
DOI: 10.25781/kaust-g4905
Language: English
Open Access status: green
OpenAlex ID: W7214056539
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