92 Product focus | Antennas prototyping, r&d or small-volume orders with atypical customisation needs. Similarly, metal additive manufacturing (AM) is continuing to rise in popularity for prototyping (and in rare cases, batch manufacturing) of antenna elements with extremely complex geometries. Plastic AM can similarly make short work of enclosures, fittings and other parts for prototypes, while injectionmoulding and vacuum-forming machines are valued for repeatedly producing such parts in bulk, although AM is increasingly leveraged for small production runs of plastic antenna components as advancements in professional AM tech have made it cheaper in some cases than making a mould that would only be used for small-to-medium-sized batches. When it comes to putting all the different antenna components together, soldering of coaxial connectors and board-mount components must increasingly be performed to IPC-A-610, widely regarded as the highest standard of end-product acceptance criteria in consumer and high-reliability PCB assemblies. This includes hand soldering, inductive soldering, reflow soldering and even semi-automated resistance soldering (increasingly used for soldering connectors at high volume). Beyond this, processes such as coaxial cable stripping, crimping, glueing, mechanical fastening, packaging, painting and engraving will also be performed with close QC to keep consistent product quality, particularly when complexity and order times are especially stringent. QC across all stages also helps to review and update production designs, layouts, machines and materials, all of these being potentially vital for lowering costs or shortening manufacturing times, while maintaining (or even improving) antenna quality and performance. Once off the production line, it is increasingly common for 100% of units to go through multiple rounds of final inspection and testing to check that performance targets will be met in the field. Testing and validation Tests performed on antennas – whether prototypes, reference models for manufacture, or mass checks or spot checks of finished units – generally fall into one of three categories. One is pattern and gain testing, in which the antenna’s radiation pattern and gain are precisely measured in a controlled environment (usually an anechoic chamber) to evaluate its ability to direct and focus energy at range during real-world missions. In the US, facilities for pattern and gain tests must be traceable to, and compliant with, standards set by the National Institute of Standards and Technology (NIST). Another is electrical testing, which gauges impedances, return losses and standing wave ratio (a parameter indicative of an impedance mismatch between the load and the internal impedance on the transmission line or waveguide, which can reduce power efficiency). A VNA is key to measuring these, and thus verifying that each unit will perform as needed at mission frequencies. Lastly, environmental tests for shock, vibration, temperature and immersion across environmental chambers, rate tables and other well-established machinery are critical to certifying that antennas will last for their promised MTBF across the combination of mission, shipping and storage conditions, and unexpected physical or weather impacts. As the effects of climate change worsen, uncrewed vehicles will need to endure worse extremes of temperature, precipitation, immersion, and so on, placing increased pressure on the manufacturers and integrators of antennas (and other components that typically mount external to vehicle hulls) to keep performing well under such conditions. Future antenna technologies Antennas evolve as an intersection of multiple scientific disciplines and industries – including radio, GNSS and cellular technologies – with various commercial, civil and military imperatives that stand to influence what tomorrow’s antennas must be designed for. For instance, of particular interest to defence integrators is advanced beam steering, which enables antennas to dynamically direct their beams towards a receiver or away from sources of spoofing or jamming. Of similar importance are null steering technologies, which create nulls in the direction of jammers to greatly reduce their efficacy against uncrewed vehicles. Antennas with such capabilities can now be made small and lightweight enough to integrate on a variety of UAVs, but these often function in just one or two bands. The development of triple-band, null-steering antennas is now in progress and expected to yield fruit within the next year or so. As both commercial and military vehicles operate in increasingly June/July 2024 | Uncrewed Systems Technology GNSS antennas engineered for new constellations, such as GPS L5 and Galileo E6, will improve position accuracy and signal strength, while reducing the threat of spoofing (Image courtesy of Trimble)
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