86 Product focus | Antennas to undertake high speeds and dynamic manoeuvres, and the antenna maker is not informed of this, then the antenna might not be designed correctly to maintain signal continuity and strength. Designing and optimising the perfect antenna for myriad mission requirements and vehicle specifics entails covering a great many antenna-specific parameters beyond perennial constraints such as SWaP-C, packaging and IP rating. Its bandwidth will change based on operational requirements: a narrowband antenna works for minimal data transmission over longer distances, such as in remote monitoring and control of commercial applications. For moderately higher data rates, a wide-band antenna may be necessary, but for very high rates, such as realtime video, Lidar or sonar streaming, the antenna’s frequency range will be dictated by a combination of regulatory, environmental and operational needs. Close understanding of the mission profile will help in choosing or tuning the antenna’s azimuth and elevation beamwidths. These define the angular range over which it radiates or receives energy efficiently, and hence the coverage area and directivity of its data links. Collectively, these qualities are vital to maximise an antenna’s gain, or how well it converts input power into radio waves in a specific direction during transmission, and radio waves received from a particular direction into electrical signals during reception. All these qualities will be influenced by the maximum RF power that the antenna can handle, which can be governed by regulations but will also affect communications consistency at range. Polarisation Polarisation, the direction of EM fields produced by the antenna, and hence the direction in which energy moves away or is received by it, is a factor of antenna success that is widely discussed in our previous features. Each of the established forms of polarisation finds its use among uncrewed vehicles. Circularly polarised antennas, for example, where the RF wave rotates as the signal propagates, can be applied in operations with air-to-ground links where orientation between a UAV and its ground control station (GCS) can vary. Linear polarisations, whether vertical or horizontal, are commonly seen in omnidirectional antennas used for LOS communications. Some modern multiple input, multiple output (MIMO) configurations now integrate more than one omnidirectional antenna to achieve both vertical and horizontal polarisation simultaneously, covering off the nulls in the doughnut-shaped radiation pattern. In addition, there has been increased interest recently in multipolarised antennas, which can passively achieve multiple combined polarisations in a single-input antenna element, thereby enabling consistent data links in dynamic environments and networks without having to resort to the complexity, size and power of active beamforming MIMO arrays, or the limitations of a singularly polarised antenna. As of writing, one of the most successful, multipolarised antenna designs uses a 3D copper element (as opposed to 2D patch antennas or 1D monopoles) that is handmade precisely to capture multiple frequencies. June/July 2024 | Uncrewed Systems Technology The design of a UAV bears heavily upon an antenna’s optimal construction, specs and placement for minimising data-link failures down the line (Image courtesy of Octane Wireless) Selecting the right antenna polarisation is crucial to maximising performance between GCS and UAV in the field (Image courtesy of Doodle Labs)
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