By November 25, 2019 Read More →

Harnessing sea change: Navigating the mega-constellations

In the present seas of change in the satellite telecommunications sector it is important to know how to navigate. Every discussion you have regarding future communications architecture will very quickly get into the sheer number of permutations of orbit, data rate, modulation scheme, optical versus radio, that small matter of clouds, latency, backhaul, revisit times, capacity, and the list goes on. The tidal forces can very quickly pull you under, to say nothing of the effect it will have on your product marketing strategy.

Safely standing on the shore, the visionaries focus on the end user and the fact that the data user in a remote location doesn’t care where their 5G signal comes from, they just want it to all be seamless. The visionaries are right, of course, but it doesn’t make the technology decisions underlying it any easier and there are rogue waves out there where cost, lifetime and technology maturity all meet.

Efficient use of resources

In these conditions, Honeywell Global Space Systems has decided to focus on its seaworthiness as well as spaceworthiness, reasoning that regardless of mission architecture the limited traffic resources on the spacecraft will need to be targeted to where the demand is. Almost regardless of architecture, there will be a desire for efficiency by avoiding unused fixed spot beams over empty ocean. The key enabling technology that underpins all of this is ever more efficient switching, being able to hop your capacity into the beams for the ground locations where it is needed, known as beam-hopping.

There are parallels to be drawn with the way in which our electronics industry has already been revolutionised by the valve, then the transistor and onwards into microelectronics. The corresponding evolu-tion in radio switching has resulted in many types of switch, the smallest of which appear in our mobile phones, the RF MEMS switch, but at much lower powers than we’re talking about on the transmit side of a telecommunications satellite.

Ferrite switches

Honeywell’s solution for beam-hopping uses ferrite switches, which take advantage of that quirky bit of physics that makes radio waves unique – their electromagnetism. We can exploit this property by making them choose between two paths simply by a magnet’s polarity at the heart of the switch junction, and make this happen very quickly using a large electric field.

The elegance of this solution is that there are no moving parts and there is no opportunity for the radio waves to bounce back from the switch, which can endanger the transmitter – in the radio world, we call this high isolation. The low losses of radio power inherent in this design of switch is also critical when you start to aggregate switches in a matrix where four or five layers may be required to route the signal to the right place.

Design considerations

While, in principle, this very simplified view makes this sound straightforward, there are many trades and considerations to be taken into account to assure reliable functionality in the harsh environment of space. It takes a lot of expertise to get it just right. Honeywell has specialised in RF payload switches in the UK and Canada since the late 1980s, with our sites in Aylesbury, England and Edinburgh, Scotland being at the forefront of this highly specialised technology throughout.

Honeywell technology from the UK has recently enabled a significant Earth observation mission for determining sea state, in the real world, not just meta-phorically. The interferometric KaRIn instrument, on the SWOT mission, is due for launch in September 2021 and uses those same switching technologies at its core. KaRIn is by far the most complex RF instrument ever built, which has delivered some major technological advancements that translate directly across to beam-hopping in telecommunications.

No one can profess to know exactly what the future holds in our rapidly evolving community but we have every confidence that Honeywell technology will continue to be at the core of the next generation of telecommunications, climate, meteoro-logical and navigation satellites.

Author Chris Bee is customer business manager at Honeywell Aerospace UK

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