Inside Frequency Control

The Role of RF Engineering in LEO Satellite Constellations

Posted by Bliley Technologies on Mar 21, 2017 6:30:00 AM

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Satellite technology has redefined how the world communicates, conducts business, and even gets from point A to point B. Millions of people take advantage of the global positioning system (GPS) network to help them navigate their way on the road every day. But how often does the average person stop and wonder how their car’s navigation system actually works?

GPS devices, satellite phones, certain TV providers and more rely on satellites in orbit around the planet to transmit and receive the signals which allow them to do their jobs. The larger the coverage area, the more satellites are required to make sure there are not gaps in service. That’s why satellites are launched and operate in groups called constellations. These networks of satellites work together to provide coverage for users all over the globe. In this article, we’ll explore the essential role that RF engineering plays in making this amazing technology possible, and how new innovations in radio frequency tech could significantly increase the capabilities of constellation satellites.

Constellation Satellites & Their Uses

Satellites have been in use since the late 1950s. In the mid-1960s, satellite network designs were developed in which multiple satellites would work together to perform a specific job. Over time, both the constellation satellites themselves and the networks became more sophisticated. To date, some 6,000 man-made satellites have been launched into space, many of them operate as constellations owned and operated by governments and private companies.

These constellation satellites are used for a wide variety of applications, including satellite radio services such as Sirius XM, and satellite television transmission. Another well-known example of a satellite constellation is the Iridium network, which consists of 66 low-earth orbit satellites spread across 6 different orbital planes, all working together to provide voice and data coverage for satellite phones and other devices.

Navigation is another obvious use. The previously mentioned GPS network was launched by the United States government and consists of 32 constellation satellites in a medium-earth orbit which work in concert to provide navigation services for civilian and military users. There are plans to replace the existing constellation with advanced GPS-III satellites, which will offer much greater accuracy, as well as security against jamming. Other nations and political entities have their own Positioning, Navigation, and Timing (PNT) systems as well, such as the Russian GLONASS and the European Union’s Galileo network. These networks are also composed of constellations to provide service to their users.

As the private sector continues to expand into space, more complex and commercially-focused constellations will continue to be launched. One of the newer applications for constellation satellites is making wireless internet accessible all over the world from space. Companies like OneWeb and Space X are competing to take the lead in this market. OneWeb’s proposed network will consist of 2000 small constellation satellites that will beam down wireless internet to every corner of the world. Space X’s network is slated to consist of nearly 4,500 satellites. It remains to be seen who will gain the upper hand in this new, private-sector space race.

Frequencies for Constellation Satellites

All of these constellations mentioned above use the radio frequency spectrum to send and receive their signals, traditionally between 3 and 30 GHz. As more and more devices and systems are crowding up the radio frequency spectrum and the demand for bandwidth increases, different spectrum ranges that have not been used as much in the past will have to be exploited. New constellation satellites will make use of the Ku and Ka frequency band range. Each of these offers the potential for much greater bandwidth, but also come with their own challenges.

Ku-bands run 12–18 GHz and have been in use for a longer period of time. Ku band ranges are about half the frequency of Ka-band (26.5–40 GHz), require larger satellite dishes, and offer less throughput. Ka bands are touted by some as the wave of the future for RF technologies since they offer superior performance and can make use of much smaller dishes. However, Ku-band does retain a significant advantage in that it is more resilient against atmospheric interference caused by rain and other poor weather.

As it stands now, Ka-band systems promise to offer faster download and upload speeds. Ku-band systems are less expensive and more dependable, but are slower and operate in a more congested frequency range. Over time, improvements in technology such as High Throughput Satellite (HTS) systems will allow higher frequency Ka-band to beam through poor weather more effectively and may help close the gap between Ku and Ka-band systems in this regard.

Constellation satellites running on Ka-band frequencies will become more common in the near future. Space X, for example, will make use of Ka-band in their quest to beam super-fast internet across every inch of the world. Ku-band isn’t going anywhere, though; OneWeb plans to use it for their equally ambitious plan for global Wi-Fi.

Regardless of which frequency range is used, constellation satellites require the highest quality crystal oscillators to perform as intended with minimal noise. At Bliley, we’ve designed and built the best oscillators on the market for 85 years and counting. Reach out to us today let us know how we can help your company bring their space-based vision into reality.

RF Engineering

Topics: satcom, RF Engineering

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