Abstract
This paper reports the effect of seawater conductivity on gain, efficiency and resonant frequency of a hemispherical helical antenna. The size of the copper ground plane for the hemispherical antenna can be reduced using conductive seawater as part of the ground plane for the antenna. Seawater increases the gain from 6 dBi to 8 dBi but with a decreased efficiency. The simulated radiation efficiency of the antenna on water surface is 61%. This paper also reports the design of a low cost floating buoy. The buoy provides a waterproof setup for the circuitry and antenna. The buoy can be effectively used for shallow water coastal monitoring.
Highlights
Recent technological advancement in oceanic engineering has helped in exploring the ocean world
The simulated radiation efficiency for the antenna on the water surface was calculated as 19.5%. These results show that water as ground plane results in a significant reduction of radiation efficiency
The buoy includes a hemispherical antenna with a small ground plane
Summary
Recent technological advancement in oceanic engineering has helped in exploring the ocean world. This paper reports how seawater conductivity can be used to our advantage if the sea surface forms part of ground plane of a hemispherical antenna. A circular copper ground plane lies horizontally on the axis of the sphere where the upper hemisphere is the antenna and the lower hemisphere contains the electronics and sensing equipment. In vacuum forming, as the heated plastic takes the shape of the mould under test, a 3D printed hemisphere with antenna indentations was designed in SolidWorks [18], using the same design parameters as that used in CST modeling. The radiating element (copper wire, see Fig. 1 and Fig. 2) was glued into this indentation This structure protects the antenna from seawater and weather conditions. The lower part of the hemisphere holding the low power transmitter and ground plane was 3D printed with ABS material.
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