Insight | Space Explained: what is the satellite spectrum used for?


Space Explained: what is the satellite spectrum used for?

  • Satellite communications rely on what is known as the radiofrequency (‘RF’) spectrum. This spectrum is divided into many different frequency bands. The choice of bands depends on many factors, including the specific applications.
  • This article discusses the frequency bands currently used by the Inmarsat satellite network and their uses. Other networks operated by Viasat, which recently acquired Inmarsat, use others.
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If you have ever been on cruise ship, an airplane or made a journey using an online map, you may have knowingly benefitted from satellite services. But satellites are integral to everyday life in ways that may be far less obvious – from enabling the shipping of goods to air traffic control.  And you may be completely unaware of the technical work that goes on behind the scenes.

Satellite communications are complex and rely on what is known as radiofrequency (‘RF’) spectrum.  This spectrum is divided into many different frequency bands, with the choice of band depending on many factors—including the specific application at issue. Annalisa Iacono, Senior RF (Radio Frequency) Antenna Engineer, explains more.

WHat does "frequency" mean?

In simple terms, the frequency of an RF signal refers to the number of times the underlying wave oscillates per second, much like the oscillation you can see in the waves at the beach. Frequency is measured in Hertz (Hz), with 1 Hz being equal to one cycle per second.  This unit can be used for all the waveforms in the entire electromagnetic spectrum - which includes everything from gamma rays, x-rays, visible light, microwaves, and radio waves. 

The higher the frequency, the faster the waves appear to move, and the more data can be transmitted per second. However, higher frequencies also mean shorter wavelengths (that is the length between the start and end of each wave), which can lead to a reduction in the strength of the signal over a distance (called signal attenuation) and an increased risk of signal interference. 

The Inmarsat satellite network currently uses microwave signals within the range of between 1 GHz and 40 GHz. There are also other bands higher up the spectrum, but in this article, we will focus on the most commonly used. The 1-40 GHz range is further subdivided into several frequency bands. Let's take a closer look at the characteristics of each such band…. 


Chart of the Radio Frequency spectrum (RF) displaying the different frequency bands and relevant applications used within satellite communication networks

L-band frequency

The L-band is the lowest frequency spectrum band that we use in our services, and is typically defined as ranging between 1 GHz and 2 GHz. L-band spectrum has a long wavelength (around 30 cm at 1 GHz), which for technical reasons means it can penetrate obstacles like storm clouds or heavy rain. This makes it extremely reliable for sending and receiving signals.

The Inmarsat L-band network is used for global maritime and aviation safety services, including by more than 200 airlines around the world. The L-band is also used for navigation, including GPS and satellite radio systems, around the world.  

S-band frequency

The S-band is typically defined as ranging between 2 GHz and 4 GHz. It is commonly used for satellite communications, including to support television and radio broadcasting.

S-band frequencies are also used for radar systems and some satellite navigation applications. We launched an S-band satellite in June 2017, which is currently used to support the European Aviation Network.  

C-Band Frequency

Further up the frequency spectrum is the C-band. This band is typically defined as ranging between 4 GHz and 8 GHz.

It is heavily used for satellite-powered television broadcasting and also used for some radar systems.  

Services in higher frequency bands 

As noted above, higher frequency bands normally permit higher data transfer speeds.  This is true of satellite offerings in the following bands.

For example, the X-band is typically defined as ranging between 8 GHz and 12 GHz, and the Ku-Band is typically defined as ranging between 12 GHz and 18 GHz. Both are commonly used around the world for a range of high-throughput communications applications, including applications using military, emergency, and government communication systems. 

The K-band is typically defined as ranging from 18-26 GHz, while the Ka-band is typically defined as ranging from 26-40 GHz (the defined ranges can vary by country). The Ka-band is commonly used to support the provision of broadband internet services and the operation of certain military and government communication systems.  

Notably, our Ka-band network is used by airlines to offer inflight WiFi, shipping companies to allow seafarers to video chat with family members from the oceans, and by aid organisations for rapid communications during humanitarian crises.  More broadly, the Ka-band is used by Viasat to support the provision of a range of services including Government communications, in-flight Wi-Fi, and satellite internet. 

About the author

Annalisa Lacono is a senior RF antenna engineer at Viasat.

After her PhD in antennas, she has spent the last 11 years working in the field of antennas for satellites, previously at a manufacturing company (ADS) and more recently, since 2020, she joined the Space Segment team (CTO) in Inmarsat (now Viasat).

Her responsibility involves following all activities related to the design, manufacturing and testing of the antennas on the satellite, from procurement to In-Orbit Testing and beyond.