Radio waves

Viasat: Radio waves and how satellites use them







February 11, 2022Alex Miller

Radio waves and how satellites use them

Understanding the basics of radio waves and frequency bands is key to understanding satellite internet technology

In 2012, UNESCO dedicated February 13 as “world radio dayThe idea is to celebrate the many ways in which radio brings us together, acknowledging the fact that it remains the most consumed medium across the globe.

And while World Radio Day is usually focused on the messages that radio brings, we thought it would be a good time to revisit this article which looks at radio from a satellite perspective.

Many people don’t even know that satellites send and receive information via radio waves, and as it becomes increasingly clear that the satellite will play an outsized role in helping to connect unconnected people around the world, it is useful to find out how it works.

At the very heart of any type of wireless communication is the use of radio waves to carry information. The basics of how it works haven’t changed much since Guglielmo Marconi sent the first radio signals in 1895, but there are a few details about how the satellite uses radio that are helpful in understanding the technology.

Here are some things you should know about how radio communications work:

Waves: Electromagnetic radiation (EM radiation) travels in waves at the speed of light. Unlike waves that travel through sound and water, electromagnetic waves require no support. They can move through the air as well as through the vacuum of space.

Frequency: The frequency of a wave is measured in Hertz (Hz). 1 hertz equals one cycle per second of the wave, shown here:

The electromagnetic spectrum: It refers to the range of all types of electromagnetic radiation, which is a form of energy. The difference between one end of the spectrum and the other is determined by the frequency of the waves. Visible light makes up part of the EM spectrum, as do radio, X-rays, and gamma rays.

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Frequency bands: This term simply refers to the chunks of wavelengths that make up the spectrum. Ka band, often used for satellite, is a type of band. Visible light is another. Some bands are quite wide, while others may only have a small portion of “bandwidth”.

Unit prefixes

Here’s what some of the most common prefixes mean, whether applied to watts, bytes, hertz, or other units

Kilo

Thousand

Mega

Million

Giga

Billion

Tera

trillion

An AM radio operates at a frequency between 535 and 1605 kilohertz (kHz), so an 800 kHz station has cyclic waves 800,000 times per second. A signal from a Ka-band satellite operates at a much higher frequency of about 28 gigahertz (GHz), 28,000,000,000 times per second.

Amplitude: This is a measurement of the height of a wave. Along with frequency and wavelength, it is one of the main characteristics of a wave.

Satellite spectrum: Satellites operate in particular areas or “bands” of the spectrum, some of which you can see here. The higher you go in frequency, the wider the bands become and the more information you can carry. Viasat mainly operates in the Ka band, in the 28 GHz range. Most satellite TV operators use the lower frequency C or Ku band because the data stream only goes in one direction and does not require as much bandwidth. However, when information needs to be sent back and forth, more bandwidth is needed for the communication to work efficiently. These higher bands are good for transmitting data, but as you go up in frequency, the complexity of the equipment increases.

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These higher frequencies are also more prone to interference – usually referred to as “attenuation”. Unlike shorter wavelengths, they do not pass through solid objects like walls, and rain can also affect the signal. For the Ku and Ka bands, this is largely due to the fact that the water molecules are approximately the same width as the wave. The satellite solves this problem by using external antennas and line-of-sight facilities. Although heavy rain or snow can still affect the signal, the effect is usually short-lived due to the duration of the heavy weather.

Additionally, ground-based technologies using these higher bands of the spectrum can use smaller antennas since high-frequency signals can be focused more efficiently.

For satellite communications, different bandwidths are useful for different applications. For satellite broadband, higher frequencies work better to transmit more data. Viasat uses several different frequency bands for our services: L-band for maritime applications, Ku-band for some aeronautical applications, and Ka-band and higher for aviation, residential and more.

Our global constellation of ViaSat-3 satellites, slated for launch in the next few years, will operate in Ka-band, as will the rest of our fleet. These next-generation satellites will have enormous data-handling capacity, with each ViaSat-3 satellite expected to have over 1 terabit per second of capacity.

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ViaSat Inc. published this content on February 11, 2022 and is solely responsible for the information contained therein. Distributed by publicunedited and unmodified, on February 11, 2022 14:57:04 UTC.

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