The more elements included, the more complex the RF architecture becomes, and additionally, in an active array, power and thermal requirements also then increase. Unsurprisingly, RF electronics generate heat, and managing that heat becomes increasingly important as antenna designs become more compact. For terminals intended for COTM or other applications where size and power are constrained, simply adding more elements is not necessarily the best option.

There can also be diminishing returns. Additional elements bring more RF components and control circuitry, along with the power and thermal overhead that comes with them. At some point, the extra complexity may not deliver a proportional improvement in useful link performance. Conversely, going too far the other way and limiting the design to a narrow electronic scan range may restrict its usefulness in a multi-orbit environment. The design challenge is therefore to find the right balance between aperture, gain, scan performance, sidelobe control, power consumption, thermal management, physical size, and cost.

When it comes to designing a network, the seemingly highest-performing array on paper may not be the most appropriate design for a specific network, particularly when achieving that performance requires a substantially larger aperture, significantly more power or results in unnecessary complexity.

Mechanical assistance provides another way of mitigating scan loss. Rather than requiring the phased array to perform at the extremes of its electronic scan range, a mechanical mechanism can physically reposition the antenna towards the satellite. This type of system can reposition the antenna over a wide range while the phased array provides the rapid beam steering needed to track the satellite. The result is an antenna in which the mechanical and electronic elements each perform the task they are best suited to, reducing the burden on the array itself, thereby also reducing scan loss.

This hybrid approach reduces the amount of electronic steering required and keeps the array closer to its broadside position, where its performance is strongest and most controlled. In a multi-orbit network, this method can be used to help the antenna move between LEO, MEO and GEO without requiring the phased array to operate continuously at extreme scan angles.

Final thoughts

As the ground segment adapts to support a multi-orbit landscape, the ability to maintain a reliable link while moving between very different geometries is set to become increasingly important. Antenna manufacturers are tasked with meeting users’ evolving needs in terms of beam performance, while also balancing those needs with the practical constraints of size, power, thermal management and cost.

Seamless multi-orbit operation cannot be guaranteed on the basis of a single measurement such as maximum gain or scan range; what matters is how consistently the antenna maintains good performance across its entire operating range. Operators must therefore look beyond broadside measurements and consider how gain, cross-polarisation and sidelobes behave at every scan angle that is relevant for the intended application. Getting a complete picture of how an antenna performs is, however, easier said than done, particularly when measurements and specifications are often inadequate or inconsistent.

This makes comprehensive testing and clearer, standardised specifications all the more important, because it gives operators a better basis for comparing antennas and understanding what they can expect in real-world deployments. As FPA technology continues to develop, we’ll likely see improved components and new concepts coming to market. Yet even with these advances, consistently delivering a strong, controlled beam across the required operating range will still require manufacturers to effectively balance the different factors that influence antenna performance.